Trays is the plural of tray.
loaves is a plural noun in the rule 8
The plural form of two-year-old is two-year-olds.
eights, 8s
8s or eights.
The plural of two is twos. e.g. Three twos are six.
Isthmi is plural. There are actually two plural forms. I will list them from singular to plural. Isthmus - Singular Isthmi - Plural Isthmuses - Plural
two
It is plural: one innings, two innings.
Two. Quizzes is the plural form of quiz.
The plural of jumbo is jumbos. As in "the two jumbos flew by".
Members IS a plural.