Th

A digraph? Is that what you mean-- two letters that represent a single sound?

Actually, I wanted the word for the contractions 'th/nd/st/rd' as used at the end of numbers - 1st, 2nd,third,fourth...

Thanks for replying. Hope you can send me an answer.

It's just the suffix for the ordinal number, with the numeral replacing the rest of the word (seventh = 7th). I suppose you could call the whole structure a contraction. My dictionary calls 'th' a symbol.

Was hoping there would be a name for it...Becomes a little difficult when one wants to vocalise it. For eg. when you specifically don't want someone to use it. Lots of people wrongly use it with roman numerals ( IVth), which is wrong. If there's no specific word for the 'th', I find it a little awkward to say, "Don't use the th". Anyway, do let me know in case you come across something.