(A proofreader's note regarding “since”)

While “since” may yet conjunctive be,

It does not coordinate.

Subordinating is its role

When linking friends that date.

No comma sits before such acts

Of joining clauses dear.

A comma shows they're coordinate;

With “since,” there's no such pair.

Especially when it means “because,”

No comma is allowed.

But negative intros/nonessential bits

With commas are endowed.

And since can have two other roles,

As adverb, preposition;

“Continuing from a known time past”—

The latter's fine rendition.

“The little dog is still incensed

Since finding skunk at fence;

Whene'er the scent of skunk is sensed,

Our dog will take offense.

“And since the skunk was at the fence, 

There lingers yet a stench;

And that is quite important since

Our dog will want revenge.

“So raucous a barking there was had,

The skunk we've not seen since.

Unrequited threat sometimes is sad;

Our dog may grief evince.”

*The key:

“Since finding skunk at fence…” (prepositional phrase)

“since the skunk was at the fence…” (subordinating conjunction, moved to the beginning of the sentence)

“since our dog will want revenge…” (subordinating conjunction)

“The skunk we've not seen since…” (adverb)

“Whene'er…” (like since, whenever is a subordinating conjunction; moved to the beginning of the sentence)