Could vs. Should

Couldverb

conditional of can

Couldverb

Used as a past subjunctive (contrary to fact).

Couldverb

Used to politely ask for permission to do something.

Couldverb

Used to politely ask for someone else to do something.

Couldverb

Used to show the possibility that something might happen.

Couldverb

Used to suggest something.

Couldnoun

Something that could happen, or could be the case, under different circumstances; a potentiality.

Could

Was, should be, or would be, able, capable, or susceptible. Used as an auxiliary, in the past tense or in the conditional present.

Couldverb

past of can

Couldverb

used to indicate possibility

Couldverb

used in making suggestions or polite requests

Couldverb

used to indicate annoyance because of something that has not been done

Couldverb

used to indicate a strong inclination to do something

Shouldverb

(auxiliary) Be obliged to; have an obligation to; indicates that the subject of the sentence has some obligation to execute the sentence predicate or that the speaker has some strong advice but has no authority to enforce it.

Shouldverb

(auxiliary) ought to; speaker's opinion, or advice that an action is correct, beneficial, or desirable.

Shouldverb

(auxiliary) Will be likely to (become or do something); indicates a degree of possibility or probability that the subject of the sentence is likely to execute the sentence predicate.

Shouldverb

Used as a variant of the present subjunctive.

Shouldverb

(auxiliary) shall

Shouldverb

A variant of would when used with first person subjects.

Shouldnoun

A statement of what ought to be the case as opposed to what is the case.

Should

Used as an auxiliary verb, to express a conditional or contingent act or state, or as a supposition of an actual fact; also, to express moral obligation (see Shall); e. g.: they should have come last week; if I should go; I should think you could go.