posted by John .
1. They work on Saturday mornings.
2. They work in the mornings.
Is the use of plural nouns, mornings, in the sentences above grammatical?
In (1) it is OK to use the plural "mornings" to distinguish the situation from working on one or a few Saturday mornings only.
In (2), use of the plural is ungrammatical and not advised. It would imply that they work every morning, with no holidays, weekends or vacations.