The difference between Proper and Utter

When used as adverbs, proper means properly, whereas utter means further out.

When used as adjectives, proper means suited or acceptable to the purpose or circumstances, whereas utter means outer.

Utter is also verb with the meaning: to say.

check bellow for the other definitions of Proper and Utter

Proper as an adjective:

Suitable. Suited or acceptable to the purpose or circumstances; fit, suitable. Following the established standards of behavior or manners; correct or decorous.

Examples:

"the proper time to plant potatoes"

"a very proper young lady"
Proper as an adjective:

Possessed, related. Used to designate a particular person, place, or thing. Proper nouns are usually written with an initial capital letter. Pertaining exclusively to a specific thing or person; particular. In the strict sense; within the strict definition or core (of a specified place, taxonomic order, idea, etc). Belonging to oneself or itself; own. Portrayed in natural or usual coloration, as opposed to conventional tinctures. Being strictly part of some other (not necessarily explicitly mentioned, but of definitional importance) thing, and not being the thing itself. Eigen-; designating a function or value which is an eigenfunction or eigenvalue.

Examples:

"usex [[proper subset]] — [[proper ideal]]"
Proper as an adjective:

Accurate, strictly applied. Excellent, of high quality; such as the specific person or thing should ideally be. (Now often merged with later senses.) Attractive, elegant. In the very strictest sense of the word. Utter, complete.

Examples:

"Now that was a proper breakfast."

"When I realized I was wearing my shirt inside out, I felt a proper fool."

Proper as an adverb (UK, colloquial):

properly; thoroughly; completely
Proper as an adverb (nonstandard, colloquial):

properly

Utter as an adjective (now, _, poetic, literary):

Outer; furthest out, most remote.
Utter as an adjective (obsolete):

Outward.
Utter as an adjective:

Absolute, unconditional, total, complete.

Examples:

"utter ruin; utter darkness"

Utter as a verb (transitive):

To say

Examples:

"Don't you utter another word!"
Utter as a verb (transitive):

To use the voice

Examples:

"Sally uttered a sigh of relief."

"The dog uttered a growling bark."
Utter as a verb (transitive):

To make speech sounds which may or may not have an actual language involved

Examples:

"Sally is uttering some fairly strange things in her illness."
Utter as a verb (transitive):

To make (a noise)

Examples:

"Sally's car uttered a hideous shriek when she applied the brakes."
Utter as a verb (legal, transitive):

To put counterfeit money, etc., into circulation