English verb conjugation
COULD CHECKMATE

Regular verb: checkmate - checkmated - checkmated

Affirmation

Simple form	V-ing form
I could checkmate you could checkmate he could checkmate we could checkmate you could checkmate they could checkmate	I could be checkmating you could be checkmating he could be checkmating we could be checkmating you could be checkmating they could be checkmating
Perfect	V-ing perfect
I could have checkmated you could have checkmated he could have checkmated we could have checkmated you could have checkmated they could have checkmated	I could have been checkmating you could have been checkmating he could have been checkmating we could have been checkmating you could have been checkmating they could have been checkmating

Negation

Simple form	V-ing form
I could not checkmate you could not checkmate he could not checkmate we could not checkmate you could not checkmate they could not checkmate	I could not be checkmating you could not be checkmating he could not be checkmating we could not be checkmating you could not be checkmating they could not be checkmating
Perfect	V-ing perfect
I could not have checkmated you could not have checkmated he could not have checkmated we could not have checkmated you could not have checkmated they could not have checkmated	I could not have been checkmating you could not have been checkmating he could not have been checkmating we could not have been checkmating you could not have been checkmating they could not have been checkmating

Interrogative form

Simple form	V-ing form
could I checkmate? could you checkmate? could he checkmate? could we checkmate? could you checkmate? could they checkmate?	could I be checkmating? could you be checkmating? could he be checkmating? could we be checkmating? could you be checkmating? could they be checkmating?
Perfect	V-ing perfect
could I have checkmated? could you have checkmated? could he have checkmated? could we have checkmated? could you have checkmated? could they have checkmated?	could I have been checkmating? could you have been checkmating? could he have been checkmating? could we have been checkmating? could you have been checkmating? could they have been checkmating?

Interro-negative form

Simple form	V-ing form
could I not checkmate? could you not checkmate? could he not checkmate? could we not checkmate? could you not checkmate? could they not checkmate?	could I not be checkmating? could you not be checkmating? could he not be checkmating? could we not be checkmating? could you not be checkmating? could they not be checkmating?
Perfect	V-ing perfect
could I not have checkmated? could you not have checkmated? could he not have checkmated? could we not have checkmated? could you not have checkmated? could they not have checkmated?	could I not have been checkmating? could you not have been checkmating? could he not have been checkmating? could we not have been checkmating? could you not have been checkmating? could they not have been checkmating?