title_body: Conlang where the initial consonants of words have meaning? A lot of languages, both natural and constructed, mark things like part of speech, gender/noun class, tense, and what not with suffixes. But what about prefixes?
  
  I think that would make more sense for a head-first language. But the issue with just adding vowels to the beginning of all words makes things look repetitive, and also adds an additional syllable.
  
  An alternative would be to have the initial consonant instead be a prefix. Though this would mean that every root in the language would have to start with a vowel (unless the language was very liberal with initial consonant clusters).
  
  I don't know of any language that does this. Its common for languages to have the rhyme of a word mean something, but I've never heard of the onset of the word meaning anything.
  
  And yes, I'm aware of the 'consonant mutations' of the Celtic languages, but those are triggered by agreement. They can't indicate anything on their own, as far as I know.
  
  I'm not saying that all conlangs have to be like natlangs, but in my experience, there's some things that languages do where there's a very good practical reason why they do them. If you come up with something that no natlang does, there may be a good reason for that. Humans for example seem to favor placing the subject of the sentence at the beginning. If you say try to place the verb first, you end up with a lot of weird problems. Of course, there are verb-initial languages, but they're rare and tend to feature very exotic grammars (Tagalog comes to mind).
upvoted_answer: Many languages mark things like those you mention at the beginning of a word. Noun class in Swahili and the other Bantu languages comes to mind. It doesn't require all roots to begin with a vowel; the prefixes also include vowels (as in Kiswahili).
  
  Russian has prepositions (not prefixes) such as в, which are pronounced as part of the onset of the following word (and it does sometimes cause initial consonant clusters), in addition to case. There's no reason why a conlang couldn't have the same as a prefix for gender, case or tense.
  
  You might also want to look at the WALS chapters Prefixing vs. Suffixing in Inflectional Morphology, Position of Case Affixes, and Position of Tense-Aspect Affixes for lists of languages that have these features as prefixes.