Oh great. I have to ask in English to get it past StackExchange filters. Characters with radicals typically have pronunciations close to the bare character. For example: "韦“ (wei) versus "伟“ (wei) or "敢“ (gan) versus "憨“ (han) But "也" (ye) and "他“ (ta) are very much exceptions. Why?
有部首旁的汉字的发音通常按照没有部首旁的字。 例如 “韦”/”伟“、 “清”/“青”、 “敢”/“憨”等。
但是 “也”/“他” 根本在例外。为什么？
Please refer to Old Chinese reconstructions when analysing phonetic components of characters.
他 - Baxter-Sagart OC: /*l̥ˤaj/ > MC: /tʰɑ/ > Mandarin Pinyin: tā
也 - Baxter-Sagart OC: /*lAjʔ/ > MC: /jiaX/ > Mandarin Pinyin: yě
有部首旁的汉字的发音通常按照没有部首旁的字。
You should probably learn that 部首 is a dictionary indexing tool, and has nothing to do with the functions of character components.
有部首旁的汉字的发音通常按照没有部首旁的字
well, this assumption is incorrect
an example:
潢．熿．獚．璜．磺．穔．簧．蟥．趪．鷬 and 黃, all share the same pronunciation wong4
http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/search.php?word=黃
so, what about
it has the component 黃 in the bottom part. unfortunately, this one is pronounce as hung4
http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/search.php?word=黌
the moral is: don't assume the pronunciation of any chinese character.
Words "come" and "become" pronounce similarly. So you think "也" and "他" should also make like this way, right?
This is no Chinese thinking mind, if you study more, you will see lots of similar samples, even "己" and "已" are different on pronunciation and meaning also.
(yeah, right, downvote. Don't write your own researched writing, just press a button. Boooooo!)
Okay, you folks all missed it. (by the way, @peter : "di" sounds somewhat like "ta", see below).
Turns out that 《也》 has an amazing history, and has taken on three distinct meanings over that annoying "five thousand years of Chinese history" that you always hear about. The morphology is simply amazing.
The modern "also"《也》(ye) is somehow a bastardization of《亦》(yi)...It is unclear how this happened, but you can see how they KIND-A look the same.
In ancient chinese, you didn't say
Oranges are fruit
you said:
Oranges this, fruit that
橙是果也
Here, 《也》is a completely different word from the modern character. In the ancient meaning, it was "that", and was pronounced closer to "ta". Hence《他》("ta") for "him" and 《地》 ("di") for ground.
Along the way, the 《也》 got dropped, leaving just 《是》 (shi), which then became "is", if only because the "that" part of the sentence disappeared, so what the heck, why not?
《也》as "that" is in itself a loan character from the very EARLY Zhou Dynasty era, when "concept words" repurposed mostly unused characters. Turns out Oracle Bone-era Chinese writing was centered on pretty basic stuff ("will it rain?", "will my cow die?"), so most characters were pretty basic.
文 and 字
These characters were referred to as 《文》, and tended to be actual pictographs, while fancy stuff made up of multiple characters glomed together were referred to as 《字》. Hence the term 《文字》. In fact, 《文》is itself a 文, and 《字》 is itself a 字！
Fun Tangent
《愛》(ai), "to love" Is an early 字. It didn't mean "hey gal, I luv ya!", it meant to lovingly take care of someone or something, and was a picture of a mother taking her toddler out for a walk (even wearing his cute little baby booties if you can believe it!!!), with a heart thrown in to show the care implied.
Back to the story...
During Zhou, scribes needed to write down concepts which didn't have 文 ... how else were they going to write the various classics? They couldn't just go on and on about cows, rain and meat, so they had to do SOMETHING.
So they borrowed 文 that SOUNDED like the concept words they needed to write down. It appears that they didn't modify sound-alike characters, they just reused them! So for a period of time, a character had two meanings: the "down home" 文 meaning like "dustpan"(《其》) or "scorpion" (《萬》), and the conceptual meaning like "them" or "10,000". The likelihood of using "dustpan" and "that group over there" was pretty small. So it kind-a worked. But still,
...that's not confusing at all...
When the "radical" system was invented later, the original "down home" use of the 文 was often remapped to a 字,with a radical attached to provide category meaning (yeah, yeah, yeah, I know radical is a lookup method...shaddap already...). So 《其》 became 《箕》 by adding a bamboo radical (so now you know what dustpans were made out of back then!)
Sometimes, the ancient, down home 文 use was just lost, and another word and/or character took the "down home" meaning.
But what about 《也》?
I don't mean to leave you with a cliffhanger, but sadly, I won't be telling you what the actual oracle bone-era meaning was, will let you look up yourself...it's pretty...ummmm, surprising. So much so that caused quite a bit of stir over the years as embarrassed scholars tried to deny it. In fact, you can still see the "NO NO NO NO, THAT'S NOT RIGHT!" annotations added to the ancient dictionaries.
To this day, the down home meaning was somewhat controversial, with a nonsense definition of "water pail" being insisted upon. But the real meaning is pretty well accepted now.
The end.
Here are some examples of ancient characters (古文) that lost their down home meanings, and how they got replaced with 字. Note that the first example looks like a 字, but it's really a 文.
文: modern/ancient meaning, down home meaning, replacement 字
萬：10k, scorpion, 蠆
其：conceptual theirs/his/that stuff over there, dust pan, 箕
為: to be/for/etc., monkey (or possibly elephant), 猴 (or possibly 象)
也：also/concrete "that", <redacted>, <redacted>
PS: For those who don't know what "down home" means, it's a southern US term for backwoods, countryside things. In Chinese, you'd say 《土》.
References: (require knowledge of Chinese)
没有部首旁的字?