Suffix
(no longer productive) Used to form nouns from verbs of action.
berth, birth, blowth, drawth, flowth, growth, sight, spilth, stealth, tilth, theft, weight
(no longer productive except jocular coinages) Used to form nouns from adjectives.
breadth, chillth, coolth, dampth, dearth, depth, filth, health, height/heighth, illth, length, roomth, ruth, strength, troth, truth, sloth/slowth, warmth, wealth, width, wrath, wrength, youth/youngth
-th
Used to form the ordinal numeral when the final term of the spelled number is not “first”, “second”, or “third”.
the 4th/Fourth of July
(mathematics) Used to form a term denoting the ordinal numeral corresponding to the value, being a natural number, of a mathematical expression.
The nth term of a geometrical progression whose first term is a and common ratio is r is given by ar.
-th
(archaic) A variant of -eth, used to form the archaic third-person singular indicative present tense of verbs.
come → cometh
have → hath
do → doth
say → saith