In indoeuropean languages the words that sound similar often denote related concepts. Is the situation similar in tonal languages? Are there languages that use a different tone to make an adjective out of a noun, for example?
Bantu languages are particularly known for exploiting tone pattern as morphemes, so just as two words (noun versus adjective, past versus habitual) can be indicated by segmental affixation, grammatical differences can be signalled with just tone differences. For example, in Logoori, [vákáráange] means "that they fry" (a verb form) and [váꜝkáráángé] is "frying (ones -- people)", an adjective. Usually, though, category-changing derivation is in part signalled by a segmental affix, but in this case there is a tense suffix /ɪ/ that happens to be the same as the adjectival suffix /ɪ/ (and you can also use /ʊ/ for adjectives, which has no verbal equivalent).
In Croatian which is a Slavic language (so Indo-European also) and is tonal too, there are some words that are written and spoken same, difference being only the tone of the vowel.
For example (note the signs above letter u which indicate type of tone, they are normally not written in a text except if there is ambiguity):
- lȕk (IPA: /lûk/) 'onion'
- lȗk (IPA: /lûːk/) 'arch'
The two grave accents above u (ȕ) indicate short falling stress. The arch above u (ȗ) indicates long falling stress.
There is also another example:
- sȃm (IPA: /sâːm/) 1. 'alone, sole' 2. 'unaided, by myself'
- sȁm (IPA: /sâm/) first person singular present tense enclitic form (short form, full form is jesam) of biti ('to be')
This gives rise to interesting sentences, for example:
- Ja sam sam. 'I am alone.'
This one can appear very often so usually there is no ambiguity, but nevertheless in written texts (formal - books, subtitles and similar, not SMS, IM, forums, etc.) they will usually be written like this:
- Ja sam sȃm.
Note the second sam with a small arch above a, it indicates that this sam means 'alone' in this case. You can also drop pronoun ja (because the form of the verb itself indicates that it is a first person) so you have a perfectly valid sentence (note that the order of sams is now reversed):
- Sȃm sam.
You can also have something like this:
- Sȃm sam napravio. 'I did it by myself.'
This indicates that the first sam means (in this case) 'by myself'. The pronoun ja is dropped because it is not needed since form of the verb already indicates it is a first person.
There are some more examples where the tone of a vowel can change the meaning of the word, but they are actually very rare in (Serbo-)Croatian. To be honest, this two (and one more which I didn't write about) are the only ones I could think of right now.