-'a' augmentative

This suffix indicates that what the noun refers to is bigger, more important, or more powerful than it would be without the suffix.

SuS wind, breeze SuS'a' strong wind

Qagh mistake Qagh'a' major blunder

woQ power woQ'a' ultimate power

-Hom diminutive

This is the opposite of the augmentative suffix. It indicates that what the noun refers to is smaller, less important, or less powerful than it would be without the suffix.

SuS wind, breeze SuSHom wisp of air

roj peace rojHom truce, temporary peace

These two suffixes are not simply equivalent to tIn/mach, but create a new concept, often requiring an entirely different English word to translate, eg. loD/loDHom man/boy, bIQ/bIQ'a' water/ocean. 

-oy endearment

This is an infrequently used, but nonetheless very interesting noun suffix. It is a very peculiar suffix because it is the only suffix that begins with a vowel rather than a consonant. (Though there are no examples, it is suspected that for those few nouns which end in a vowel, ' is inserted before this suffix.) The suffix usually follows a noun referring to a relative (mother, father, etc.), but it could also follow a noun for an animal, especially a pet, and means that the speaker is particularly fond of whatever the noun refers to. It is strongly suggested that non-native speakers of Klingon avoid this suffix unless they know what they are getting into.

vav father vavoy daddy

be'nI' sister be'nI'oy sis

Canon outside TKD

Q (from Quvar): KGT uses naQHom "little cane/staff" to refer to the stick used to hit percussion instruments. What is the difference between a naQHom and a naQ mach? Similarly, KGT also uses bo'Dagh'a' and bo'DaghHom for "big/little scoop". What is the difference between a bo'Dagh'a' and a bo'Dagh tIn? I know that -Hom and -'a' also refer to concepts besides size, like importance, power, intensity, etc., but I feel like none of those concepts besides size really apply to sticks, staves, and/or scoops, so I'm uncertain of where the distinction lies. More generally, are there ever situations or nouns where -Hom/-'a' are more or less synonymous with mach/tIn, or is there always some inherent conceptual difference?

A (from Okrand): -Hom (rather than mach) is used when physical size is not a distinguishing factor (or not the only one or the main one). But, having said that, it's also used for some common items that could equally well be modified by mach. naQHom is the normal term for percussion stick because, somehow or other, that became common usage. The stick used for percussion instruments could totally properly be called a naQ mach, but a naQ mach could be any little stick, not just one for hitting percussion instruments. Note that in a non-musical context, naQHom could refer to some stick of lesser importance; in a musical context, however, the most likely meaning would be the percussion stick.

Q (from Quvar): Are the words loDHom and be'Hom considered too childish and "inferior" to be applied to HojnIypu', or can they be used for teens and young adults as well? Do Klingons simply use loD and be'? Or do they say 'young man' and 'young woman'? Or do they have their own words?

A (from Okrand): Just use loD and be'.

This is not a grammatical question, but one of usage (embedded, of course, in culture).

The English words "girl" and "boy" prompted the question. Both of those English words refer to young females and males, respectively, of course, but they are also used in all sorts of other situations, some neutral, some affectionate, some demeaning (and not everyone agrees on which is which). In any case, it's not just a matter of age.

In Klingon, a be' is a female of any age and a loD is a male of any age. To specifically refer to a younger one of these, add -Hom. You probably wouldn't use -Hom for anyone past the Age of Ascension, but whatever other usage patterns there may be are subtle and murky. In general, if you're not talking about children (however defined), stick with be' and loD.