God/goodness/Heaven knows

God knows

1. No one knows (except for God). God knows how long it will take for my application to be processed. A: "How do you think you did on your exam?" B: "God knows!"
2. It is absolutely true, certain, or definite that; it is obvious or clear that. God knows I need to do well on this test or I can kiss my scholarship goodbye!
See also: god, know

goodness knows

1. No one knows. (A variant of "God knows.") Goodness knows how long it will take for my application to be processed. A: "How do you think you did on your exam?" B: "Goodness knows!"
2. It is true, certain, or definite that; it is obvious or clear that. Goodness knows I need to do well on this test, or I can kiss my scholarship goodbye!
See also: goodness, know

heaven knows

1. No one knows (except for God or the heavens). Often emphasized as "heaven only knows." Heaven only knows how long it will take for my application to be processed. A: "How do you think you did on your exam?" B: "Heaven knows!"
2. It is absolutely true, certain, or definite that; it is obvious or clear that. Heaven knows I need to do well on this test or I can kiss my scholarship goodbye!
See also: heaven, know

God knows

Also, goodness knows; heaven knows.
1. Truly, certainly, definitely, as in God knows I need a winter coat. This expression, which originated about 1300 as God wot, does not necessarily imply that God is all-knowing but merely emphasizes the truth of the statement it accompanies. The variants using goodness and heaven are euphemisms that avoid taking God's name in vain. [Second half of 1500s]
2. Also, God only knows. Only God knows, that is, neither I nor anyone else knows, as in God knows where I've stored those photos, or God only knows how many people will join the march. [Second half of 1500s]
See also: god, know

God/goodness/Heaven knows

(spoken)
1 I do not know; no one knows: ‘What’s going to happen next?’ ‘God knows.’
2 used for adding emphasis to a statement, opinion, etc: God knows how he manages to survive on such a small salary.I’m no gardening expert, goodness knows!(Some people may find the use of God knows offensive.)
See also: god, goodness, heaven, know