English verb conjugation
COULD SAIL

Regular verb: sail - sailed - sailed

Affirmation

Simple form	V-ing form
I could sail you could sail he could sail we could sail you could sail they could sail	I could be sailing you could be sailing he could be sailing we could be sailing you could be sailing they could be sailing
Perfect	V-ing perfect
I could have sailed you could have sailed he could have sailed we could have sailed you could have sailed they could have sailed	I could have been sailing you could have been sailing he could have been sailing we could have been sailing you could have been sailing they could have been sailing

Negation

Simple form	V-ing form
I couldn't sail you couldn't sail he couldn't sail we couldn't sail you couldn't sail they couldn't sail	I couldn't be sailing you couldn't be sailing he couldn't be sailing we couldn't be sailing you couldn't be sailing they couldn't be sailing
Perfect	V-ing perfect
I couldn't have sailed you couldn't have sailed he couldn't have sailed we couldn't have sailed you couldn't have sailed they couldn't have sailed	I couldn't have been sailing you couldn't have been sailing he couldn't have been sailing we couldn't have been sailing you couldn't have been sailing they couldn't have been sailing

Interrogative form

Simple form	V-ing form
could I sail? could you sail? could he sail? could we sail? could you sail? could they sail?	could I be sailing? could you be sailing? could he be sailing? could we be sailing? could you be sailing? could they be sailing?
Perfect	V-ing perfect
could I have sailed? could you have sailed? could he have sailed? could we have sailed? could you have sailed? could they have sailed?	could I have been sailing? could you have been sailing? could he have been sailing? could we have been sailing? could you have been sailing? could they have been sailing?

Interro-negative form

Simple form	V-ing form
couldn't I sail? couldn't you sail? couldn't he sail? couldn't we sail? couldn't you sail? couldn't they sail?	couldn't I be sailing? couldn't you be sailing? couldn't he be sailing? couldn't we be sailing? couldn't you be sailing? couldn't they be sailing?
Perfect	V-ing perfect
couldn't I have sailed? couldn't you have sailed? couldn't he have sailed? couldn't we have sailed? couldn't you have sailed? couldn't they have sailed?	couldn't I have been sailing? couldn't you have been sailing? couldn't he have been sailing? couldn't we have been sailing? couldn't you have been sailing? couldn't they have been sailing?