What is the word used to describe a particular type of sound made with language?

I believe you are looking for phoneme as here:

The smallest phonetic unit in a language that is capable of conveying a distinction in meaning, as the m of mat and the b of bat in English.

Update:
Writing systems that compose the tokens of language by describing the sounds use what are termed phonetic writing systems, in contrast to pictographic and ideographic writing systems such as are commonly used in much of East Asia.

It is really quite impossible to know what you’re actually asking here, because you are misusing a lot of concept and words.

1. Language does not make sounds; humans make sounds that combine to make (or be) language.
2. Characters and letters don’t make sound either; they are various types of attempts at trying to represent the sounds made by humans when using language, in a way that can be written down on a piece of paper (or carved into wooden tablets or stones, etc.). They do not necessarily actually represent anything at all.

The reason it seems like different characters/letters can produce different sounds in different words is that they can. Letters are just abstract representations of the sounds used in language. Since writing (unlike speech) is usually intended to enable communication between people far apart, speaking different dialects and sometimes even different languages, it has always been important that written language be more or less codified into some kind of written standard. These standards are not as quick to evolve as the spoken language, exactly because they are artificial and have to be learnt by the users: if they changed as constantly and quickly as the spoken language, everyone would have their work cut out for them just trying to keep up and learn the new forms.

As such, spoken language can often change quite drastically, while the written language stays (almost) the same. English, for example, went through a massive sound change a few hundred years ago, called the Great Vowel Shift, which has had an enormous impact on how English words are pronounced—but the writing system remained more or less unchanged. Since this vowel change meant that what was once just a simple vowel [a] could now have become at least three or four different vowels (depending on the context it was originally found in), and since the spelling did not change, you eventually had a system where the letter ‹a› can stand for a whole bunch of different sounds.

The most important point: This has nothing to do with ‘language’ as such. Language is a spoken thing, the thing we use to speak to each other. Writing is not ‘language’, it is a secondary abstraction of language, and it does not ‘make’ sounds. It only attempts (usually quite poorly) to represent them.