Korean verbs are typically classified into four categories: action, state (or description), existential, and the copulas.
[2] Grammatical categories of verb suffixes include voice (passive or causative), tense (past, present, or future), aspect (of an action – complete, experienced, repeated, or continuing), honorification (appropriate choice of suffix following language protocol), and clause-final conjunctives or sentence enders chosen from various speech styles and types of sentences such as interrogative, declarative, imperative, and suggestive.
A great many verbs change the pronunciation of the final consonant of the root after the addition of a suffix.
Their structure when used as the predicate of a clause is prefix + root + up to seven suffixes, and can be illustrated with a template: I Valency may be passive or causative.
Future tense & prospective aspect is key-ss 겠 -get-, past perfective is -e⁄a-ss 었/았 -eot-/-at but with vowel harmony.
If there is no intervening consonant, this reduces, both in pronunciation and in writing: a-ss to 았 at-, and wa-ss to 왔 wat-.
V The syntactic moods, for lack of a better term, are the indicative -nun 는 -neun, -ni 니, or n ㄴ; the retrospective (imperfective) -ten 던 -deon, ti 디 -di, or t ㄷ -d-; and the subjunctive si 시 -si or s ㅅ.
None of these are used in the casual or intimate styles, and the formal plain indicative declarative can only occur in the gnomic tense.
Derivational endings are attached directly to the verb root, and are followed by the tense suffixes.
These derivational suffixes end with the high vowels i ㅣ or wu ㅜ which is reduced to a glide in the long stem form.
Such verbs are used, for example, when speaking of one's elders, one's social superiors (parents, teachers, bosses), or strangers.
Following the derivational endings, Korean verbs can contain up to three suffixes in a row which represent a combination of tense, aspect, and mood.
Etymologically, 'ss is a contraction of the existential verb iss 있 via vowel absorption.
A verb can superficially have two copies of the above-mentioned suffix, the second of which, however, is always -ess 었 -eot and represents a true past tense.
Because this infix is occasionally used for a conditional, or inferential tense, depending on context it is sometimes called irrealis.
(In the Korean writing system hangul, the ㅂ is written at the bottom of the previous syllable.
)[8] This shows deference towards the audience of the conversation, for example when speaking in a formal situation, such as to (but not necessarily about) one's elders.
The syntactic moods, for want of a better term, are indicative -nun 는 -neun, -n(i) 니/ㄴ; retrospective (imperfective) -ten 던 -deon, -t(i) 디/ㄷ; and jussive -s(i)시/ㅅ.
None of these are used in the casual or intimate styles, and only the formal plain indicative declarative can occur in the gnomic tense.
The pragmatic moods, for want of a better term, are the declaratives ta 다, la 라, and ey 에; interrogatives kka 까, ya 야, and ka 가; propositive ta 다, -ca 자, and -ey 에; and the imperative o 오, -e⁄a la 어라/아라, and -key 게.
The structure is ROOT + valence + attributive suffix, with little of the complexity of finite verbs above.
Active verbs use the attributive suffix 은 -eun after a consonant, or -n ㄴ after a vowel, for the past tense.
For descriptive or stative verbs, often equivalent to adjectives in English, this form is used for generic (gnomic) descriptions; effectively, "eaten food" is food which once was eaten (past), whereas "a pretty flower" is a flower which has become pretty, and still is (present/timeless).
For example, from the verb 먹 meok "to eat", the adjective 예쁘 yeppeu "pretty", and the nouns 밥 bap "cooked rice" and 꽃 kkot "flower", we get: The perfective suffix 었 -eoss- is sometimes used as well, with the same meaning, on active verbs.
Another suffix, somewhat similar in meaning, is 서 -seo which is, however, attached to the long stem of a verb ending in -e⁄a.
consists of only a verb because the context in which this sentence would occur makes the identity of the arguments obvious.