(A proofreader's note regarding “affect” and “effect”)

“Affect,” “effect,” both words of change,

Confuse in use though set with clues;

There's “a” for “action," “e” for “end";

They clear the views, not just amuse.

“Affect” will serve most oft as verb,

The part of speech with “actions” linked.

“To influence/cause effect upon”

Is meaning main that's heard and inked.

“Effect” would rather be a noun;

It rarely functions as a verb.

“Effect,” the noun, says “outcome caused,”

Though other meanings may usurp.

“Affect” begins, “effect” it brings,

With “a” for “action,” “e” for “end,”

Reminding what as verb comes first,

The alphabet being faithful friend.

And when as verb “effect” would act,

Its focus helps to set apart.

It emphasizes what is caused,

While with “affect,” we get the start.

“Affect” as noun is seldom found

Yet known in special fields of study—

One's underlying emotional state,

Out-picturing also there already.

“'It will affect the daily take,'

Was her retort to great effect;

Affected by her strong response,

The others voted to reject.”

“Then after change effects a change,

Effective change has had effect.

Affected by effective change,

One's affect changes to reflect.”

(A proofreader's note regarding “derisive” and “derisory”)

“Derisory” was first of the infants in nursery;

“Derisive” arrived in due course;

Since standing nearby was “derision” as parent,

Some differences puzzled their nurse.

“Derisive” would speak of “conveying or causing

Contemptuous ridicule/scorn.”

“Derisory,” the elder, surprisingly mellow,

Went further afield to adorn.

Instead of describing the thing that was mocking,

“Derisory” put focus elsewhere;

The object of mockery itself was the target,

“Inviting derision” to wear.

A clue to this difference in meanings as stated

Is found in the suffixes carried.

The “ory” of one hints a less direct function

In adjectives busy and harried.

Most “ive”-bearing adjectives act as descriptors 

Of traits found inherent in nouns.

With “ory,” more likely, a function or purpose

Is what it describes on its rounds.

In commonplace meaning, “derisory” stresses

“Inadequate/piffling in nature,”

Which then is inviting of scorn or of mockery,

Delivered by nouns with that feature.

Quite sadly, however, “derisory” sometimes

Is taken as saying “derisive.”

We know that these words although sharing a cradle

Are different in ways most decisive.

“Though stolidly entered, the sum was derisory,

And comments derisive ensued.

The manager frowned, and derisive guffawing

Was nipped in the bud as too rude.”

(A proofreader's note regarding “extant” and “extinct”)

First “extant” from “standing out,”

Adjective only in its stance;

“Still existing,” “not destroyed,”

Meanings fair with half a chance.

Then “extent” might lesser be,

With its “e” instead of “a”;

But “extend” in family tree

Gives this noun a greater say.

Next “extinct” the adjective

Waves its wand—a curse to cast;

From “extinguish,” none should live,

Left to molder in the past.

“Once extinguished, then extinct,

Yet a flame may live again.

Once distinguished, then distinct,

Yet such fame may need refrain.

“Once extinct, no chance extant,

Not there standing evermore.

This 'extinct,' no small extent;

Full its measure, ever sure.

“If extant, beware extent

And of life rejoicing be.

Coming end may some resent

If, indeed, that's all they see.”

(A proofreader's note regarding “insidious” and “invidious”)

“Insidious,” “invidious”—the words of our study—

Are actors infrequent today.

There nevertheless are some roles that do favor

The talents they bring into play.

Though wearing their costumes with only slight difference,

They claim to tell stories distinct.

It’s quickly confirmed by a look at their origins—

A hint that the two are not linked.

“Insidious” in meaning when traced back in Latin

Is “ambush-like,” clearly and true.

“Invidious,” instead, springs from “ill will” and “envy,”

With “invi” from “envy” as clue.

“Insidious” has friends in “deceptive” and “subtle,”

And speaks of a gradual amassing

Of harmful or adverse effects that are hidden,

Revealed in their final undressing.

Another sense given is “harmful but tempting,”

“Seductive” then granted as well.

“Awaiting a chance to ensnare” (as in ambush)

Comes next as the last sense to gel.

“Invidious” expresses no sense of a “hiding,”

Regardless of usage as “envious”;

“Unpleasant by nature” and  “apt to cause ill will”

Do, likewise, say “harmful not devious.”

“They only suspected insidious insiders 

When statements invidious were sent.

Their source was well hidden, for none of the members

Admitted invidious intent.”

(A proofreader's note regarding “farther” and “further”)

Though “farther” and “further” have vowels distinct,

Their functions and meanings are mostly the same;

They both serve as adjective, adverb as well,

Comparatives of “far” although different in name.

As adverbs, their senses are equally used,

Relating to literal and figurative spans.

They say “to a greater degree or extent,”

Or “at or as far as a point that's advanced.”

“More distant” is one sense the adjectives have;

Another is “going/extending beyond.”

This latter from “farther” has sought to abscond,

Discovering with “further” a much stronger bond.

This meaning, “additional,” is one of the points

Where “farther” and “further” are different in use.

There's also the adverb, conjunctive in type:

“Moreover,” “in addition,” whichever you choose.

Despite being like “farther” in much of its usage,

“Further” is favored when distance is absent.

Of interest as well is that more parts of speech

Are given to “further” by common assent.

“We run ever farther to further our joy,

Proceeding most strongly and, further, with verve.

We further the skeptics or simply annoy,

But all will be certain that farther's no verb.

“Remember that further is broader in scope,

'Additional,' 'moreover,' both there in its clime.

When ‘far’ is compared by extent or degree,

Then further beats farther, its reach more sublime.”

(A proofreader's note regarding “abstruse” and “obtuse”)

“Abstruse” and “obtuse,” with costumes that confuse,

Follow disparate purviews and missions;

Though each in the other may see an excuse,

As descriptors they serve different passions.

Apart from its use in some specialty areas,

Like geometry, botany, and such,

“Obtuse” as an adjective speaks most of people,

But sometimes on things it will touch.

A Latin ancestor had “blunt” as its meaning,

So “dull” and “not pointed” we find.

But “lacking a quickness or sharpness of intellect”

Likewise is often in mind.

“Obtuse” in its usage extends to describing

A thing that is not clearly stated;

By virtue of this, it comes close to “abstruse,”

But the two words should not be conflated.

The word “comprehensible” conjures the key

To the meanings “abstruse” may adopt;

“Hellacious to understand due to complexity

While clear in expression and apt”;

Thus, “difficult” for persons of normal intelligence

Or “clear to enlightened ones only.”

Instead, with “obtuse,” a deliberate dull-wittedness

Sometimes is meant although phony.

“Remember 'abstract' before choosing 'abstruse'

To misuse of 'obtuse’ make unlikely.”

“If person 'obtuse' should claim things as 'abstruse,'

It's a ruse to refuse—and quite rightly.”