Korean/Verbs

Introduction
Most Korean dictionaries list verbs (동사) in a form that ends in 다(da):

Verb stems
Like English verbs, Korean verbs change their endings and take auxiliary words to fit the tense (when an action occurs) and mood (statements vs. commands vs. questions) of the situation. However, Korean verbs also change form to express honorifics and speech levels in order to reflect the social relationships between the speaker, the subject, and the audience. The speech level listed in most books (including dictionaries) is called 해라체. It is formal but of low to neutral politeness. The 해라체 speech level is sometimes used by close friends, relatives of similar age, and young people. As shown above, the indicative forms of verbs in the 해라체 speech level end in 다. The part of the word preceding 다 is called the "verb stem".

Exercise
Identify the verb stem of the following verbs:

Honorifics
Korean grammar expresses the relationship between the speaker, the subject, and the listener by using honorifics and speech levels in conjugation and word choice. Honorifics express the speaker's relationship and politeness or social humility toward the subject of the sentence, and speech levels to express these to the audience. When talking about someone of superior status, one must indicate their superiority by using special honorific affixes. Generally, someone is considered superior in status if he or she is an older relative, a stranger of roughly equal or greater age, an employer, a teacher, a customer, or the like. Someone is looked upon as equal or inferior in status if he or she is a younger stranger, a student, an employee or the like.

Note: If the subject is considered inferior to the listener, the honorific should not be used, as the misuse of honorifics or the use of inappropriate speech levels is likely to be considered insulting, or hilariously disrespectful.

A few Korean verbs have special honorific equivalents, but most can be converted into an honorific form by adding an honorific affix after the stem and before the ending.

If the verb stem ends in a vowel, add 시,

but if it ends in a consonant, add 으시.

Thus, the honorific form of 가다 ("to go") is 가시다 and the honorific form of 걷다 ("to walk") is 걸으시다.

Exercise
Write the honorific form of the following verbs:

Formal polite speech level (합쇼체)
Since the 해라체 speech level is not polite enough for many of the initial encounters you might have speaking Korean, we will first learn a polite speech level instead. 합쇼체 is the formal, polite speech level in Korean. It is used commonly between strangers, among male co-workers, by TV announcers, and to customers.

To create statements (that is, to use the indicative mood of verbs) in the 합쇼체 form,

⋅Add the honorific affix 시 or 으시 if applicable. ⋅Then add ㅂ니다 if the result ends in a vowel or 습니다 if it ends in a consonant. E.g.:

Exercise
In this exercise, you are talking with a stranger about various subjects. Determine correct 합쇼체 form for the following verbs based on the given subject:

Informal polite speech level (해요체)
When people of similar age or social standing converse, they often use the informal polite speech level, called 해요체. 해요체 is appropriately polite for most of the situations you will typically encounter, so it is the next form to learn.

To create the 해요체 form of Korean verbs, do the following:
 * 1) Take the stem.
 * 2) Add the honorific 시 or 으시 if applicable.
 * 3) If the last letter is ㅂ, change it to 우.
 * 4) If the result ends in a vowel followed by 르, insert an extra ㄹ, making the end ㄹ르.
 * 5) If the last vowel is now ㅡ, change it to ㅏ if the next-to-last vowel is ㅗ or ㅏ. Otherwise, change ㅡ to ㅓ.
 * 6) If the last vowel is now ㅗ or ㅏ, add ㅏ요.
 * 7) If the last character is 하, add ㅕ요.
 * 8) For others, add ㅓ요.

Korean spelling rules make the above rules seem just a bit more complicated in practice:
 * If the result ends in ㅏㅏ요, that collapses to ㅏ요.
 * If the result ends in ㅗㅏ요, that collapses to ㅘ요.
 * If the result ends in ㅜㅓ요, that collapses to ㅝ요.
 * If the result ends in 시ㅓ요, that collapses to 세요.
 * If the result ends inㅣㅓ요, that collapses to ㅕ요.
 * If the result ends in 하ㅕ요, that collapses to 해요.

The usual spelling rules also apply, so an ㅏ without an initial consonant is written as 아 and an ㅓ without an initial consonant is written as 어.

Exercise
In this exercise, you are talking with a friend about various subjects. Determine correct 해요체 form for the following verbs in both honorific and non-honorific forms:

Casual speech level (해체)
When close friends and relatives talk with each other, they may use a very casual speech level called 해체. Be careful not to use this 해체 with someone with whom you are not very close, as it can be considered offensive.

Since you already know the 해요체 form, creating the casual 해체 form of Korean verbs is easy, just take the 요 off of the end of the 해요체 form:

Exercise
In this exercise, you are talking with a close friend. Determine correct 해체 form for the following verbs:

Tense
Korean verbs can be conjugated into several different tenses to indicate the time when an event occurs.

Past tense
The past tense of a Korean verb is formed as follows:
 * 1) Take the verb stem.
 * 2) Add the honorific suffix (시 or 으시) if applicable.
 * 3) Add one of the following:
 * 4) * If the word now ends in 하, add 였. Note: 하였 often is contracted as 했.
 * 5) * Otherwise, if the preceding vowel of the verb stem is ㅏ or ㅗ, add 았.
 * 6) * Otherwise, add 었.
 * 7) Add the ending for the appropriate speech level.

Exercise
Determine the honorific and non-honorific past tense forms of these verbs.

Future tense
The future tense of a Korean verb is formed as follows:
 * 1) Take the verb stem.
 * 2) Add the honorific suffix (시 or 으시) if applicable.
 * 3) Add the suffix 겠.
 * 4) Add the ending for the appropriate speech level.

Other tenses
Korean also has a remote past tense, used to indicate that an event occurred long ago, a past future tense, and a (rarely-used) remote past future tense. To form the remote past tense, first form the past tense, then add an extra 었 before the ending for the appropriate speech level.

Copula and existence verb
이다 and 있다:

Two Korean words conjugate similar to verbs and are often translated as verbs but are not considered verbs in Korean grammar: 이다 (the copula, often translated as "to be") and 있다 (the existence particle, often translated as "to exist").

Reference
Coréen/Grammaire/Verbes