There are finite number of letters. If we limit the length of a word to finite amount of letters, the number of all possible words is also finite.
If there were infinite number of letters in a word and this word consisted of infinite amount of sounds, the pronunciation of a word would never end.
As there are finite number of words, also the number of consepts formed from these words is finite.
On the other hand, if we would create consepts in mathematical way, we could have infinite number of consepts. Though, all of them couldn’t be explicitly ever written nor said in finite amount of time.
I’ve sometimes wonderd, that how many meaningful natural languages of humans’ from all of these finite number of words could be formed — also how many grammars. What we understand by “meaningful language” might be hard to define…