is there a difference between "decline" and "decrease" (with respect to grammar, word usage)

Answer 1

dimensions of difference
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If something DECLINES it becomes less in (a) quantity (b) strength or (3) importance. When something DECREASES, or when you decrease it, it becomes less in (a) quantity, (b) strength or (c) size.

usage
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quantity : The number of party members has declined/decreased.
strength : Body strength declines/decreases with age.
importance : Marxist influence has declined (not decreased) in Africa.
size : Modern computers has decreased (not declined) in size considerably.

DECLINE has two phrases with the same meaning : (a) on the decline : Many forms of organized religions seem to be on the decline. (b) into decline ; After the war, Sri Lanka's tourism industry fell into decline. DECREASE has no phrasal usage. Both the verbs have noun forms : There was a sharp DECLINE/DECREASE in population. DECLINE has another meaning : (to) refuse.

grammar
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Grammatically, DECLINE has one pattern (verb intransitive), but DECREASE has two patterns (verb intransitive and transitive)

Answer 2

Yes.
Look them up at www.dictionary.com

In general, "decline" refers to going down a literal or metaphoric slope or to refuse or turn down an offer. "Decrease" refers to reducing the amount of something.

Both can be verbs or nouns. There are situations in which they are synonyms eg: "There was a decline/decrease in sales this past month", but there are many uses where they are not synonyms.

Answer 3

Usually, qualities, such as proper grammar and word usage, decline. Amounts, such as snowfall, wind speed, number of patrons, etc., decrease.

Answer 4

Decline is usually used to turn someone down or as a steep decline

Decrease is usually used for amounts

Answer 5

Decline - go down, like losing altitude.

Decrease - become smaller by losing mass or volume.

Answer 6

industry, cities can be in decline

the stock market may see a temporary decrease i