yhdes (englanniksi)

first : ungrammatical (a: ordinal / as a single word)
corresponds "oneth" (a: ordinal)
eleventh : regular form (a: ordinal / as an ones digit in the word yhdestoista - eleventh, also occurring in larger numbers; e.g. 111th, 4311th)
-first : dated (a: ordinal / as an ones digit, which is not eleventh; e.g. 31th, 131th)
ensimmäinen preferred instead (a: ordinal)
one- : not used (a: ordinal / as a tens / hundreds / thousands / ... digit; e.g. 100th, 1000th)
because it can be omitted (a: ordinal)