which are unmarked for

[suprunp]

Table 4.17 [abridged]

present perfective (simple)
present progressive (simple)
present perfective progressive

We have already used the word 'simple' to describe a verb phrase totally
unmarked for aspect (simple present, simple past). By extension, we may
also, to avoid ambiguity, use the term 'simple' for verb phrases which are
unmarked for one of the two aspects, as indicated in Table 4.17.
(A Comprehensive Grammar of the English Language)

I wonder if it is possible to say 'which are marked for' without losing the meaning.

Thanks.

[5jj]

If you wanted to preserve the sense, you would have to say, "which are marked for one, and only one, of the two aspects..."

I have to say that I do not find Quirk et al's use of 'simple' in this way helpful. I prefer the original, and common meaning - "a verb phrase totally unmarked for aspect (simple present, simple past)."

[suprunp]

Have I understood it right that the sense in the original sentence is preserved by going from 'totally unmarked [unmarked for two] to 'unmarked for one'?

Thanks.

[5jj]

Yes.