A strict phonological definition:
Two words rhyme iff:
a) They are (last) stressed on the same syllable, counting from the end of the words.
and
b) They are pronounced identically from the vowel in their last stressed syllable to their end (using whatever pronounciation you're comfortable with).
So it is that undid and liquid are not rhyming words – I don't think anyone can make a good case for liˈquid or ˈundid. This is a complicating factor that makes English (and Spanish, etc.) poetry loads of fun: think of the difference between reˈcord and ˈrecord. In French, Finnish, Hungarian and Polish, by contrast, you can simply ignore the first rule and in other languages (Latin, anyone?) the stress can be pretty well predicted (once you know the rules) or inferred from the orthography.
Note: if you see boxes above, your browser doesn't properly support the IPA.
a) They are (last) stressed on the same syllable, counting from the end of the words.
and
b) They are pronounced identically from the vowel in their last stressed syllable to their end (using whatever pronounciation you're comfortable with).
So it is that undid and liquid are not rhyming words – I don't think anyone can make a good case for liˈquid or ˈundid. This is a complicating factor that makes English (and Spanish, etc.) poetry loads of fun: think of the difference between reˈcord and ˈrecord. In French, Finnish, Hungarian and Polish, by contrast, you can simply ignore the first rule and in other languages (Latin, anyone?) the stress can be pretty well predicted (once you know the rules) or inferred from the orthography.
Note: if you see boxes above, your browser doesn't properly support the IPA.