Pronunciation of the -ate suffix

I've noticed that a few words may be both a noun and an adjective, remain spelt the same, but change the pronunciation of -ate to ət or āt. Sometimes the meanings are related, others they are not.

For example: separate.

We separate the objects into separate categories.

We pronounce the first with āt but the second as ət.

Off the top of my head, the only other I can think of is "conjugate", though I'm fairly certain there are others that are just not coming to my mind at the moment.

Is this just coincidence or the product of some understandable process?

Solution 1:

To begin with, separāt (verb) - separet (noun) is not the only case of this. Moderāt/Moderet, or Mediāt/Immediet both go the same way: -ate is pronounced with the difference you mention even though they are spelled the same way. So does articulāt/articulet. There may be others, but so far I have not found or recalled any. The fact that I have not found any exceptions does not, however, prove that there are none. So I have no basis for saying that it is a co-incidence, though I would have to start leaning towards the idea that there might be some reason for the difference. If there is, it is likely to have something to do with the rhythm of natural speech.

One candidate would be that the various forms of the verbs (separated/articulating and even the noun moderator sit very uncomfortably in the mouth with the '-et' pronunciation. Some other nouns, like magistrate (which has not cognate verb) is actually pronounced magistrāt by some and magistret by others. So there may be some sort of physical/oral explanation. But what it is I am far from sure.

Solution 2:

I don't know about a process, but the difference in pronunciation can be interpreted as resulting from -ate verbs all having some kind of stress* on the last syllable, while -ate nouns or adjectives can have a fully unstressed last syllable.

That in turn could be explained as an example of a more general principle that Greg Lee gives in his answer to the question Why do nouns and verbs which are stressed differently all exhibit the same variation?:

Nouns and adjectives tolerate more unstressed syllables than verbs do.

*For separate, the stress on the last syllable would be a minor stress, as the primary stress falls on the first syllable. Some disyllabic -ate verbs are pronounced with the primary stress on the second syllable (e.g. create); this isn't as common in American English as it is in British English (where vibrate, migrate and narrate often take second-syllable stress).