In music theory or musicianship, when writing a rhythmic pattern, can you use any 2 notes for one syllable?

Question

I know you have to join them with a tie/slur (which is it?) if you have 2 notes for one syllable. Also you can tie/slur 2 quavers for a single syllable, but what about having a dotted quaver and a semi-quaver for one syllable?

Answer 1

I think it's called a tie.  It's a line that loops over (to connect) the notes.

Yes, dotted rhythms for one syllable can work, too.

These are called melismas (two tones for one syllable for a lyric).

Answer 2

If the two notes are the same pitch, it's a tie. If they're of different pitches, it's a slur. You may use any pitches, and any rhythmic pattern, you think someone may be able to sing--depending on the style in which you're writing.

Answer 3

Can you use any 2 notes for one syllable?

Yes you can!  Consider the Christmas song "Angels We Have Heard on High." On the chorus, the 1st syllable of the word "Gloria" has 16 notes in an extended melodic line.  It's called a melisma.