aah

drawn out sound of pleasure, relief, or relaxation; the plural is often paired with ooh for an exclamation of wonder or surprise (oohs and aahs)

ah

placeholder signifying hesitation, confusion, ignorance, or even guilt, often indicating that the speaker is thinking frantically; variations are er, uh, and um; also an interjection signifying understanding (Ah, I get it)

aha

exclamation of discovery or realization

ahh

exclamation of surprise or fright; also a variant of aah used as a sound of pleasure, relief, or relaxation

argh

exclamation of frustration, comparable to rats or drat; sometimes used for a pirate's exclamation

arrr

pirate's sound of agreement; pirate's exclamation

aw

mild exclamation of protest, disappointment, or entreaty (Aw, I didn't mean it.)

aww

exclamation over the cuteness of something

bah

old-fashioned exclamation of dismissal or contempt; compare to the contemporary word so  (Bah, who cares? Bah! Humbug!)

beh

variation of bah

blah

interjection used as filler (typically written three times) to show that either someone droned on about a topic or what had been said was predictable and/or commonplace and all parties now listening understand what was said without it being necessary to repeat what was said (And then she moaned about her husband. You know, blah blah blah.)

blech

mild to medium exclamation of disgust

blergh

an interjection of any combination of disgust, boredom, dissatisfaction, and other negative emotions; also blurgh and blargh; probably from a combination of bleh and argh and/or ugh.

bwahaha

less common variant of mwahaha; often bwah-ha-ha

criminy

mild swear word, somewhat old-fashioned; euphemism for Christ

duh

exclamation of exasperation or disdain over the explanation of something obvious

eh

mild exclamation of unconcern or indifference (Eh, who cares.); solicitation to repeat something (Eh, what was that?); question tag (You heard about it, eh?)

er

placeholder signifying hesitation, confusion, ignorance, or even guilt, often indicating that the speaker is thinking frantically; may be followed by an ellipsis (Er . . . I'm not sure.); variations are ah, um, and uh

erm

variation of er (I've never seen this in a published book that I can recall and never heard a real person say it, but it shows up in a lot of manuscripts I see)

ew

exclamation of disgust, typically over something nasty; can be made more dramatic by repeating letters (Ewww, that's foul. Eeew, that stinks.)

geez

exclamation of exasperation; a mild oath to be used in place of Jesus; also sheesh

hmm

placeholder interjection signifying that the speaker is thinking or considering a response to what has been said

hooah

U.S. Army sound of agreement or affirmation; battle cry; [pronounced hua, accent on hoo]

hooyah

U.S. Navy sound of agreement or affirmation; battle cry

huh

interjection used to signify a dawning revelation or admittance of ignorance over a piece of information (Huh, is that so.); also used as a question tag to solicit agreement (I guess this means we're leaving now, huh?)

humph

mild exclamation of disagreement or reluctant agreement; also exclamation of displeasure; variations include hmph, hrmph, harumph, harumpf, harrumph; old-fashioned and often put in the mouths of elderly men and crotchety women

hrmph, hmph, harumph, harumpf, harrumph

variations of humph

ick

exclamation of disgust; also yuck

meh

old-fashioned mild interjection of dismissal or indifference, much like beh

mm

hmm-murmur of agreement that may also indicate inattention; much like uh-huh

mmm

murmur of pleasure

mwahaha

mock-sinister laugh, often used for a villain; also mwah-ha-ha; variant is bwahaha

nah

informal no; opposite of yeah; [pronounced two ways: like the n-a in nap or the n-o in not rather than as nay]

nuh

uh-childish argumentative no; opposite of yuh-huh; [stress on uh]

oh

word signifying comprehension or surprise (often overused in dialogue); can be drawn out by repeating letters (Ohhh, it's so beautiful.);  [pronounced like the letter o]

oof

like oomph, often comic or exaggerated sound of breath being knocked from someone from a blow to the belly; [a short sound, usually not changed by adding letters]

ooh

exclamation of wonder or surprise; often paired with aah (oohs and aahs); [rhymes with Sue and dew]

oomph

sound of exhalation of breath, often after a collision (may be comic)

oorah

U.S. Marine sound of agreement or affirmation; battle cry

ow

exclamation of pain

pfft

old-fashioned sound of dismissal or unconcern (not common in contemporary fiction); also phfft

phew

exclamation of relief, often used humorously in contemporary fiction

phooey

mild interjection used to show disagreement or disbelief; also a mild curse word akin to darn or drat, but more genteel

pshaw

old-fashioned exclamation of contempt or disagreement (not common in contemporary fiction except in historicals and as deliberate reference to its use in the past); [the p is pronounced]

psst

(usually) quiet interjection used to gain the attention of someone else

sheesh

exclamation of exasperation; a mild oath used in place of Jesus; also geez

shh or shhh

command to keep quiet, often accompanied by finger to lips

shssh

variation of shhh

shush

command to keep quiet, a combination of shh and hush; more a true word than a sound

ta-da

exclamation to express success or to point attention at something

ugh

exclamation of mild disgust

uh

placeholder signifying hesitation, confusion, ignorance, or even guilt, often indicating that the speaker is thinking frantically; may be followed by an ellipsis (Uh, I think it's that one. Uh . . . I'm not sure that what you're saying is true.); variations are ah, er, and um

uh, uh, uh

command, often to young children, to stop doing something (Uh, uh, uh, don't touch that.)

uh huh

interjection signifying understanding and sometimes, but not always, agreement (use it to show someone is saying they understand what is being said even though they might not agree with what is said); informal yes; also uh-huh

uh oh

exclamation of dismay or anticipation of something bad happening; used often by young children; also uh-oh

uh uh

informal no; also uh-uh and unh-unh

um

placeholder signifying hesitation, confusion, ignorance, or even guilt, often indicating that the speaker is thinking frantically; variations are ah, er, and uh; often repeated as um, um, um (Um, um, um, I'm thinking) and stretched out as ummm

unh

unh-informal no; variant of uh uh and uh-uh

whoa

exclamation of surprise or shock (not woah)

yay

exclamation of triumph or victory (Yay, we won!)

yea

yes;  used in the context of a spoken vote; rhymes with and is often paired with nay

yeah

contemporary informal yes; opposite of nah (Yeah, I get it.); [does not rhyme with  nay, and I freely admit I don't know how to explain how this one sounds-how about a link to Merriam-Webster, which has a decent recording of the word?]

yech

variation of yuck, an exclamation of disgust

yeow

exclamation of pain, shock, or surprise; also yow

yikes

exclamation of (negative) surprise or shock; comic

yow

variation of yeow, an exclamation of pain, shock, or surprise

yowza

exclamation of pleasure or pleased surprise or a pleasant shock

yuck

exclamation of disgust; also ick

yuh-huh

argumentative or insistent childish yes; [accent on huh]; opposite of nuh-uh