Plurals רבים

The default masculine plural is ים, pronounced ־im. The default feminine plural is ות, pronounced ־ot. The singular ending ה usually drops before ות: ילדה becomes ילדות. A feminine ־ית often becomes ־יות: מכונית becomes מכוניות.

Adding a plural ending often shortens or shifts a vowel in the singular. סֵפֶר becomes סְפָרִים (sfarim); בַּיִת becomes בָּתִּים (batim). You hear the change more than you see it in unvowelled writing. Learn the plural as a second citation form, not as a mechanical suffix.

A dual ending יים still appears on paired body parts and on a few time words. ידיים, עיניים, and רגליים are the ordinary plurals for hands, eyes, and legs. שעתיים means two hours. Treat duals as vocabulary, not as a living number system you can apply to any noun.

Once the noun is plural, adjectives and present-tense verbs must be plural too. ילדים גדולים, ילדות גדולות. Do not mix a feminine plural noun with a masculine plural adjective. The noun is the boss; everything after it copies number and gender.