Korean nouns do not have grammatical gender. As for the category of number, they can be made plural by adding the suffix 들 deul to the end of the word but in general, the suffix is not used when the plurality of the noun is clear from the context.
The most basic, fundamental Korean vocabulary is native to the Korean language, e.g. 나라 (nara, country), 날 (nal, day). However, a large body of Korean nouns originates from the Korean pronunciation of Chinese characters e.g. 산(山) san, “mountain”, or 역(驛) yeok, “station” and others.
Korean postpositions, or particles, are suffixes or short words in Korean grammar that immediately follow a noun or pronoun. They are also sometimes called case markers.
Postpositions come after nouns and pronouns and are used to indicate the role (subject, object, complement, or topic) of a noun in a sentence or clause. For example, -uy 의is used to denote the genitive case.
Korean pronouns are highly influenced by the honorifics (see further in the article) in the language. This means the forms of the pronouns change depending on the social status and level of seniority of the person you are speaking to.
For example, the pronoun for "I" there is both the informal 나 (na) and the honorific/humble 저 (jeo).
In general, Koreans avoid using second person singular pronouns, especially when using honorific forms.
There are basically no pure third-person pronouns in Korean. Instead of pronouns, personal names, titles, or kinship terms are used to refer to third persons in both oral and written communication.
Korean numerals include two regularly used sets: a native Korean set and a Sino-Korean set, nearly entirely based on the Chinese numerals. The distinction between the two numeral systems is very important. Things can be counted with one of the two systems, but seldom both.
Take expressing time, for instance. The Sino-Korean numerals are used to denote the minute of time. For example, sam-sib-o bun (삼십오 분; 三十五 分) means "__:35" or "thirty-five minutes." The native Korean numerals are used for the hours in the 12-hour system and for the hours 0:00 to 12:00 in the 24-hour system. The hours 13:00 to 24:00 in the 24-hour system are denoted using both the native Korean numerals and the Sino-Korean numerals.
Korean gwanhyeongsa are known in English as "determiners," "determinatives," "pre-nouns," "adnouns," "attributives," "unconjugated adjectives," and "indeclinable adjectives." Gwanhyeongsa come before and modify or specify nouns, much like attributive adjectives or articles in English.
Korean adverbs, busa, include words like 또 (ddo, "again") and 가득 (gadeuk, "fully"). Busa, like adverbs in English, modify verbs.
Verbs in the Korean language come in the last place in a clause. Verbs are the most complex part of speech, and a properly conjugated verb may stand on its own as a complete sentence.
Korean verbs are typically classified into four categories: action, state (or description), existential, and the copulas.
The distinction between action verbs and descriptive verbs is visible in verb conjugation in a few places. The copulas conjugate like stative verbs, but the existential verbs conjugate like action verbs. Some verbs can be either stative or active, depending on the meaning.
Korean verbs are conjugated. Every verb form in Korean has two parts: a verb root plus a sequence of inflectional suffixes. Verbs can be quite long because of all the suffixes that mark grammatical contrasts (there can be up to seven suffixes attached to a verb).
Derivational endings are attached directly to the verb root and are followed by the tense suffixes. These endings include those demonstrating valency and subject honorifics.
Following the derivational endings, Korean verbs can contain up to three suffixes in a row which represent a combination of tense, aspect, and mood.
For example, the future suffix is -keyss 겠 -get, often used to describe future events. It is used, when the speaker has valid reasons to believe something will be certain to happen. For instance, the suffix is used in broadcasting contexts in Korean such as weather forecasts.
But it may be used together with the perfective and remote past suffixes, or in a present-tense context. If used with the perfective suffix, this makes an inferential or conditional past -e⁄a'ss-keyss 았겠/었겠 -eotget/-atget "should have, would have, must have."
These suffixes include suffixes denoting mood, formality, and politeness.
Attributive verb endings modify nouns and take the place of attributive adjectives. Korean does not have relative pronouns. Instead, attributive verbs modify nouns, as adjectives do in English. Where in English one would say "I saw the man who walks the dog", the structure of Korean is more like "The dog-walking man I saw".
Korean verbs can also take conjunctive suffixes. These suffixes make subordinate clauses.
Sentences in Korean follow the subject-object-verb pattern. Verbs are typically the last element in a Korean sentence, and the only one necessary. That is, a properly conjugated verb can form a sentence by itself. The subject and the object of a sentence are often omitted when these are considered obvious in context.
The relationship between a speaker or writer and his or her subject and audience is of extreme importance in Korean grammar. The relationship between speaker/writer and subject referent is reflected in honorifics, whereas that between speaker/writer and audience is reflected in speech level.
When talking about someone superior in status, a speaker or writer usually uses special nouns or verb endings to indicate the subject's superiority.
Honorifics in traditional Korea were strictly hierarchical. The caste and estate systems possessed patterns and usages much more complex and stratified than those used today. Honorifics in contemporary Korea are now used for people who are psychologically distant. Honorifics are also used for people who are superior in status. For example, older people, teachers, and employers.
There are seven verb paradigms or speech levels in Korean, and each level has its own unique set of verb endings which are used to indicate the level of formality of a situation. Unlike honorifics—which are used to show respect towards the referent (the person spoken of) —speech levels are used to show respect towards a speaker's or writer's audience (the person spoken to).
This is a very brief overview of Korean grammar. To truly master it, you will need to study each of the parts of speech in much more detail, especially the complex verb and verb suffixes system. However, this overview will hopefully give you a general idea of the Korean grammatical system and of the main points you should consider when learning.