Allen and Greenough's New Latin Grammar for Schools and Colleges
J. B. Greenough, G. L. Kittredge, A. A. Howard, Benj. L. D'Ooge, Ed.

1. dīxerit quis ( quispiam ), some one may say.
2. aliquī philosophī ita putant, some philosophers think so. [ quīdam would mean certain persons defined to the speaker's mind, though not named.]
3. “habitant hīc quaedam mulierēs pauperculae ” (Ter. Ad. 647) , some poor women live here [i.e. some women he knows of; some women or other would be aliquae or nesciō quae ].

[*] a. The indefinite quis is rare except in the combinations sī quis, if any; nisi quis, if any ... not; nē quis, lest any, in order that none; num quis ( ecquis ), whether any; and in relative clauses.

[*] b. The compounds quispiam and aliquis are often used instead of quis after sī , nisi , nē , and num , and are rather more emphatic:—

1. “quid sī hōc quispiam voluit deus ” (Ter. Eun. 875) , what if some god had desired this?
2. nisi alicui suōrum negōtium daret (Nep. Dion. 8.2), unless he should employ some one of his friends.
3. “cavēbat Pompêius omnia, nē aliquid vōs timērētis ” (Mil. 66) , Pompey took every precaution, so that you might have no fear.