Hmm… let's see what we have here. This might not be short…
I've been taking Aikido classes for about a month and have recently found a Jiu Jitsu club that trains on a different day so immediately jumped into an intro letter. There's a girl at my Aikido club that has never practised Aikido before (she's an absolute beginner like me) but she's been picking up virtually everything we're taught instantly without any flaws. She previously trained in Jiu Jitsu and our 3 blackbelts often say things like "I bet you're already familiar with this". So I've been wondering how different are the two styles?
Okay, let's start with some history, and some clarification of terminology. Probably the first thing to understand is that Aikido is Jujutsu… just a particular form of it. As such, you really can't say anything about "how different are these two styles", as, well, we aren't dealing with "two styles"… we're dealing with a huge range of differing methodologies and approaches.
Let's look at "Jujutsu" first.
What is commonly referred to as "Jujutsu" is, realistically, a rather general collection of a very wide range of different approaches to various contexts, applications, and situations. They are Japanese arts that focus on unarmed, or lightly armed, combative methods against unarmed, lightly armed, or armed opponents… but that's about where the connection ends. These systems might be more "battlefield", or "civilian"… it might be part of a larger syllabus, or be the main focus itself… it might have a weaponry contingent, or leave that completely… it might have a lot of striking, or practically none, or anything in between… it might have a large repertoire of throws, or almost none… it could focus on joint locks, or chokes… or not… it might even not be called "jujutsu"… it might be called taijutsu… or yawara… or hade… goho… torite… kogusoku… kumiuchi… katcchu yawara… koshi no mawari… judo (both the modern form, and a term used in Jikishinkage Ryu some 150 years prior to Kano)… aikijutsu/aikijujutsu… yawaragei… gyoi dori… kempo… tai… ju… wa… wajutsu… suhada jujutsu/heifuku yawara… yoroi kumiuchi/senjo kumiuchi… goshinjutsu… joshi yawara/joshi goshinjutsu… hakuda… koppo… kawami… shubaku… yawarariki… ryoku… and a whole range of others. You might have a single method taught in one system, or multiple forms taught in a single art (such as Yagyu Shingan Ryu, who have four separate curriculums dealing with different contexts and applications). In other words, "jujutsu", as a separate and distinct art, really doesn't exist… but there are many, many things that can be classified as "jujutsu".
From there, we get the ideas of koryu jujutsu (old school jujutsu, what might be thought of as "proper" jujutsu, arts that truly come from the samurai [or related], specifically pre-dating the Meiji Restoration of 1868), and gendai jujutsu (modern forms, which might be Japanese, such as Judo, Aikido, Hakko Ryu, Moto-ha Yoshin Ryu, and more, or Western, which are often Judo based, incorporating aspects of karate, aikido, or anything else, with little that actually defines it)… you get sporting versions (BJJ, Judo, and a range of Western systems), and non-sporting versions… you have systems that are largely ground work (most often modern… it really doesn't feature in classical systems, for a variety of reasons), or basically none… and, even when ground work is involved, it might be wildly different to what's seen in modern sporting systems…
As you can see, there's really no single definition of what "jujutsu" is… it just covers too much ground.
When we start to look at Aikido, it's a little more defined… but there's still quite a bit of variation involved. Aikido was developed by Ueshiba Morihei, largely out of his exposure to Daito Ryu Aikijutsu, as well as a range of other arts (however minimalist it may have been), and his increasing association with a range of spiritual awakenings and factions of Buddhism. As he continued to develop his art, various of his students went out on their own, to continue in the way they were taught. This has resulted in a range of different forms of Aikido as well… which can be very interesting to look at, as they provide clues into snapshots of time in Ueshiba's own development. For example, Shioda Gozo was the first to go his own way, and form the Yoshinkan… this faction of Aikido focuses on the type of training that Shioda experienced in the early days of Aikido, when much of it was closer to the Daito Ryu roots… at that point, Ueshiba's school was known as the "Jigoku Dojo" (Hell Dojo), largely for the amount of pain endured within it's walls… it was definitely hard, seriously applied martial training. After WWII, Ueshiba had his own series of revelations, which laid the groundwork for the later "pacifist" reputation for Aikido (it might be important to note that, earlier in his career, Ueshiba was, essentially, a right-wing "leg breaker"… hardly the pacifist ideal that many have of him…

. When Tomiki Kenji went his own way, he wanted to introduce Aikido to schools… and created a competitive format, based on knife defence, and his experience in Judo… then there are the factions of "Ki" Aikido, largely derived from people such as Tohei Koichi… there are any number of independent schools and instructors, and various national associations in a range of countries, not necessarily associated with any of the major Japanese groups… and, of course, there's the "mainline" group, who continue under the descendants of Ueshiba himself (known at various times as Takemusu Aikido, or, most commonly, Iwama Ryu, after the location it was developed in). Different lines/branches have differing levels of weaponry associated, as well as different training approaches and ideologies (large and small).
So, when you ask "how different are the two styles?", we need first to know what both of the styles are… the jujutsu, and the aikido.
From what I can gather from videos they look virtually the same with the exception that Jiu Jitsu seems to teach groundwork, which is something that so far appears to be very frowned upon amongst Aikido practitioners. Reading about Jiu Jitsu it says it involves strikes but I'm unsure if these are actually taught as offensive techniques or more as atemi like in Aikido? I know atemi was originally supposed to simulate weapons but I think we can all agree the empty hand atemi in Aikido aren't particularly realistic depictions of the kinds of strikes used in the modern world.
Hmm… again, as mentioned, far more information would be needed. But to address a few things here, groundwork isn't "frowned upon", it's simply not part of the context of Aikido… it kinda goes against a range of their methods and ideals. Striking in "jujutsu" could be anything… it could be similar to Aikido's atemi, or more of a classical jujutsu methodology… or simply borrowed/taken from something like karate… or even aspects of boxing/kickboxing. It's really hard to know without knowing the system. Oh, and there's a difference between striking not being realistic, and striking not being what is seen in a modern (Western) form of violence… the thing is, you need to understand the difference. Aikido is teaching you Aikido… not street fighting… or anything of the kind. Thinking that all forms of violence are the same, or that something has to look a certain way to be "realistic" is to head down a rather narrow path which simply leads to a deep lack of understanding of anything outside a tiny fraction of what really exists… and we already have a few here that cover that.
The spelling is correct for the style listed on the website although I am aware that there are quite a few different ways of saying/spelling jiu jitsu.. Some times it seems to be spelt differently, sometimes it's all one word, other times it's broken into two or three words. I've never been sure as to the correct spelling.
Real brief, the kanji is 柔術, which is written in hiragana (syllables) as じゅうじゅつ… to write that in romaji (Latin-based English letters), it's "jyuu-jyutsuu". The correct transliteration is "jujutsu"… however, early on in the introduction of the word/concept to English, it was often written as "jiu-jitsu" (note: the usage of hyphens is purely subjective, Japanese doesn't subdivide that way), so a number of Western versions have utilised that spelling, including Brazilian Jiu-jitsu. But, if it's a Japanese system, the only correct version really is "Jujutsu".
The club teaches "Aiuchi Jiu Jitsu" and when the instructor replied to my email he said something along the lines of "we do cover groundwork but not to the same extent as Brazilian Jiu Jitsu". By the sounds of it though Jujutsu is Japanese and Jiu Jitsu is Brazilian? As I said I wasn't sure because there's technically kana for both spellings in Japanese so it's confusing lol.
Not quite… "Jujutsu" is correctly used for Japanese systems (frankly, it should be used for all who use the kanji 柔術… but that's a large argument that's been had here too many times…

, with "jiujitsu" being used by BJJ, and other modern, Western systems. In one sense, none of those are actually Jujutsu anyway, as, despite having a lineage from them (maybe…

, they aren't Japanese systems… which is one of the defining aspects.
When it comes to this particular system, uh… well, the first thing I'll say is that the name is just really, really, really badly chosen. It means "mutual striking", and is the concept of killing the other guy, but getting killed yourself in the process. It's a bad thing, and something to be avoided, as it shows that you weren't actually aware of what was going on around you… when it comes up in a martial tradition, it's alongside warnings of how to avoid such an event… to the point that it's often given the translation of "mutual killing/slaying". A little more alarming is that the choice of kanji they use to write the name not only doesn't make sense… it also can't be pronounced the way their name is. What they use is 合中柔術… the first character is "Ai", meaning "meeting", and the last two are "jujutsu"… but the second one is "chu", or "naka"… and means "middle". So… "meet in the middle"? "Ainaka Jujutsu"? "Aichu Jujutsu"? Hmm…
So, to begin with, a very poorly chosen name, written incorrectly. Not a good start. Looking through the history of the system, there's very little definite in any of the systems it's based in… other than Judo… to the point that they talk about the fact that they have very little actual system (almost seeming proud of that… interesting…

, and to be honest, the photos on the page don't fill me with a lot of confidence… it looks okay Judo-wise, but you really can't tell from what is shown… however, the mis-mash of disparate systems and methodologies, focusing on the idea that techniques are what makes a martial art, are all things that I wouldn't recommend…
Yeahhh okay "I think we can all agree" was perhaps a little bold lol..
But seriously Aikido atemi does seem to be pretty widely criticised :/ but hey I'm pretty new to it so perhaps they'll become more refined but so far things like 'chops' to the forehead and punches with the back of the hand facing outwards to the left or right seem a bit silly.
Yeah, I'm going to side with others, and ask what you mean by a punch with the back of the hand facing out… that's actually pretty standard in many systems (if you're referring to a vertical fist on impact), to the point that it's sometimes referred to as an "Oriental Fist", as opposed to a "Western Fist" (palm down).