It was either during a Wordcraft chat or another thread a while back that I mentioned a poem I clipped a long time ago which helps a writer or speaker decide whether to use "effect" or "affect." In writing a letter recently to someone I have great respect for, I had to once again look up this pairing in the dictionary just to be sure that I had had it correct. (I did but it's comforting to see it in the dictionary.)

The following is copyright 1988 by Willard R. Espy.

You Affect Me - But to What Effect?

On sober reflection I find your affection
for me is a role you've affected. (1)
Why don't I object? Well, I like the effect (2)
on others; at last I'm respected.

You're affecting (3) a love that I'm skeptical of:
my doubts, though, I won't let affect (4) me;
You've made me a prize in the envious eyes
of women who used to reject me.

This change you've effected (5) is widely reflected --
the sneerers are now genuflecting.
Effects (6) of this kind, to a bachelor's mind,
are the sort that require no correcting.

Keep on, then-- affect (7) true affection, unchecked
by facts-- who am I to disparage?
Could you but neglect those short skirts you affect, (8)
I'd tender an offer of marriage.

1.- Simulated, pretended
2.- The result
3.- Pretending
4.- Influence
5.- Brought about
6.- Things brought about
7.- Pretend
8.- Are given to; make a point of wearing

There's also a noun, affect, which is a term from psychology meaning roughly feeling or emtion, especially its outward appearance. For example, "After her labotomy, Hedwig lacked affect.

Rather than a pre-frontal lobotomy, I'd prefer a free bottle in front o' me.

That might affect the effect of .....

Wow, I love that poem, CJ. I would have never been able to articulate all those nuances in definition. While I surely knew what was meant by each "affect" and "effect," I wouldn't have been able to discriminate the definitions like that.

Wow, that poem is very helpful. I am currently writing some software and at one point I have to output information about a process being done on various rows. So I would say "12 Rows Affected". I finally ended up calling my Dad and asking him, since he is well versed in such things, but this poem would have made my life much easier.

Of course, elsewhere in the software I'm required to work with multiple instances of an index, which are referred to as "indexes".

Quote "...which are referred to as "indexes"...."

Not indices?

Nope. Evidently I'm the only person who cares. I've seen the same thing with "Vertexes", but usually people correct themselves and say "Vertices".

I did make an attempt to push "Indices" through, but "Indexes" has become so widespread that it was too much work for one man.

There's a pretty standard usage difference: indexes are lists at the back of books, indices are subscripts across a variable.

Funny, people usually frown when I say suffices and prefices, but why stop there, and especially when I say "two apparatus".

I've heard prefices a lot, but I don't know if I've ever connected that word to prefix before. I'm sure I understood it, and just never though about it. I don't think I've every heard suffices, unless this is the same word as in "It suffices to say", in which case, "Wow, really?" is in order.

As for which to use "indices" vs. "indexes", the context I'm using could be related to either of the choices (lists or subscripts), so I'll have to dig deep and discover the etymology of the term, as which point the correct plural should be apparent.

I'm a technical writer and many of the style guides I've read have indices for the plural of index when your writing about the indices of an array or other ordered list, but indexes whence you're writing about the alphabetized list at the end of a book with page number references. (NB: many not all style guides.) As for prefices and suffices, there both the appropriate Latin plurals for prefix and suffix respectively. Likewise, codices for codex and appendices for appendix. I just like the sound, and I am not saying that these are correct or incorrect.

Interesting variations here.

American Heritage® Dictionary says the plural is ver·ti·ces (-t-sz) also ver·tex·es
American Heritage® Stedman's Medical says ver·tex·es or ver·ti·ces (-t-sz), reversing it.
Webster's Collegiate (on-line) follows the former, but Webster's Unabridged follows the later.

I haven't the temerity to check "vortex".