English verb conjugation
COULD WINNOW

Regular verb: winnow - winnowed - winnowed

Affirmation

Simple form	V-ing form
I could winnow you could winnow he could winnow we could winnow you could winnow they could winnow	I could be winnowing you could be winnowing he could be winnowing we could be winnowing you could be winnowing they could be winnowing
Perfect	V-ing perfect
I could have winnowed you could have winnowed he could have winnowed we could have winnowed you could have winnowed they could have winnowed	I could have been winnowing you could have been winnowing he could have been winnowing we could have been winnowing you could have been winnowing they could have been winnowing

Negation

Simple form	V-ing form
I couldn't winnow you couldn't winnow he couldn't winnow we couldn't winnow you couldn't winnow they couldn't winnow	I couldn't be winnowing you couldn't be winnowing he couldn't be winnowing we couldn't be winnowing you couldn't be winnowing they couldn't be winnowing
Perfect	V-ing perfect
I couldn't have winnowed you couldn't have winnowed he couldn't have winnowed we couldn't have winnowed you couldn't have winnowed they couldn't have winnowed	I couldn't have been winnowing you couldn't have been winnowing he couldn't have been winnowing we couldn't have been winnowing you couldn't have been winnowing they couldn't have been winnowing

Interrogative form

Simple form	V-ing form
could I winnow? could you winnow? could he winnow? could we winnow? could you winnow? could they winnow?	could I be winnowing? could you be winnowing? could he be winnowing? could we be winnowing? could you be winnowing? could they be winnowing?
Perfect	V-ing perfect
could I have winnowed? could you have winnowed? could he have winnowed? could we have winnowed? could you have winnowed? could they have winnowed?	could I have been winnowing? could you have been winnowing? could he have been winnowing? could we have been winnowing? could you have been winnowing? could they have been winnowing?

Interro-negative form

Simple form	V-ing form
couldn't I winnow? couldn't you winnow? couldn't he winnow? couldn't we winnow? couldn't you winnow? couldn't they winnow?	couldn't I be winnowing? couldn't you be winnowing? couldn't he be winnowing? couldn't we be winnowing? couldn't you be winnowing? couldn't they be winnowing?
Perfect	V-ing perfect
couldn't I have winnowed? couldn't you have winnowed? couldn't he have winnowed? couldn't we have winnowed? couldn't you have winnowed? couldn't they have winnowed?	couldn't I have been winnowing? couldn't you have been winnowing? couldn't he have been winnowing? couldn't we have been winnowing? couldn't you have been winnowing? couldn't they have been winnowing?