English verb conjugation
COULD DIPHTHONGISE

Regular verb: diphthongise - diphthongised - diphthongised

Affirmation

Simple form	V-ing form
I could diphthongise you could diphthongise he could diphthongise we could diphthongise you could diphthongise they could diphthongise	I could be diphthongising you could be diphthongising he could be diphthongising we could be diphthongising you could be diphthongising they could be diphthongising
Perfect	V-ing perfect
I could have diphthongised you could have diphthongised he could have diphthongised we could have diphthongised you could have diphthongised they could have diphthongised	I could have been diphthongising you could have been diphthongising he could have been diphthongising we could have been diphthongising you could have been diphthongising they could have been diphthongising

Negation

Simple form	V-ing form
I couldn't diphthongise you couldn't diphthongise he couldn't diphthongise we couldn't diphthongise you couldn't diphthongise they couldn't diphthongise	I couldn't be diphthongising you couldn't be diphthongising he couldn't be diphthongising we couldn't be diphthongising you couldn't be diphthongising they couldn't be diphthongising
Perfect	V-ing perfect
I couldn't have diphthongised you couldn't have diphthongised he couldn't have diphthongised we couldn't have diphthongised you couldn't have diphthongised they couldn't have diphthongised	I couldn't have been diphthongising you couldn't have been diphthongising he couldn't have been diphthongising we couldn't have been diphthongising you couldn't have been diphthongising they couldn't have been diphthongising

Interrogative form

Simple form	V-ing form
could I diphthongise? could you diphthongise? could he diphthongise? could we diphthongise? could you diphthongise? could they diphthongise?	could I be diphthongising? could you be diphthongising? could he be diphthongising? could we be diphthongising? could you be diphthongising? could they be diphthongising?
Perfect	V-ing perfect
could I have diphthongised? could you have diphthongised? could he have diphthongised? could we have diphthongised? could you have diphthongised? could they have diphthongised?	could I have been diphthongising? could you have been diphthongising? could he have been diphthongising? could we have been diphthongising? could you have been diphthongising? could they have been diphthongising?

Interro-negative form

Simple form	V-ing form
couldn't I diphthongise? couldn't you diphthongise? couldn't he diphthongise? couldn't we diphthongise? couldn't you diphthongise? couldn't they diphthongise?	couldn't I be diphthongising? couldn't you be diphthongising? couldn't he be diphthongising? couldn't we be diphthongising? couldn't you be diphthongising? couldn't they be diphthongising?
Perfect	V-ing perfect
couldn't I have diphthongised? couldn't you have diphthongised? couldn't he have diphthongised? couldn't we have diphthongised? couldn't you have diphthongised? couldn't they have diphthongised?	couldn't I have been diphthongising? couldn't you have been diphthongising? couldn't he have been diphthongising? couldn't we have been diphthongising? couldn't you have been diphthongising? couldn't they have been diphthongising?