The prefinal ending—tense, honorific The consonant stem is the stem having consonant at the lower part, e.g. 먹-, 울-, 웃-. The vowel stem is the opposite term, e.g. 예쁘-, 흐르-, 지-, 내리-. '으' as in 감으니, 감으며 is euphony(euphonic vowel). '-고, -더니' as in '물들고, 물들더니' are consonant endings. Prefinal endings can be divided into two categories by distribution. The following shows the endings of wide distribution. I. (A)-시- (B)-는-, -었-, -겠- (C)-옵- I(A), which has the most largest combination with other endings, forms the 주체높임법(존경법). '-시' requires euphonic vowel(매개모음) '으' if it attaches to other consonants except 'ㄹ'. I(B) generally decides the tense. '-는-' is the prefinal ending comes between a consonant stem and declarative ending '-다', whilst its allomorph '-ㄴ-' is placed under a vowel stem. Thus, the two are defined phonologically. '-는-' in exclamatory sentence '먹는구나, 먹는구먼, 먹는구려; 가는구나, 가는구먼, 가는구려' also comes under this category, so, in this case,'-는-' is defined morphologically. There's limit in distribution of usage in '-는/ㄴ-' and '-는-', but they are regarded as the prefinal endings signifying the tense since the flexible replaceability with other tense-morphemes. II. (D) 웃는다, 간다, 웃는구나, 웃는구나 cf. 웃었다, 웃겠다, 갔다, 가겠다, 웃었구나, 갔구나 etc. '-었-' is the prefinal ending used for the past tense. It follows the stem of 음성모음(ㅓ, ㅜ, ㅕ, ㅠ, ㅔ, ㅝ, ㅟ, ㅖ), whilst '-았-' follows the stem of 양성모음(ㅏ, ㅗ, ㅑ, ㅛ, ㅘ, ㅚ, ㅐ). Therefore the two are phonologic allomorph, and '-였-' following 'ㅏ, ㅗ' such as '하였-', '모였-' is morphologic. '-었-' can combine with most of endings, though it doesn't reach to that combinability of'-시-'. '-겠-' alone can make the future tense, but if it follows the ending '-었-', it signifies only the meaning of guess about the past event, and the following ending is more restrictive than '-었-'. For reference, you hear '-었-' when you pronounce '-였-' long such as 여어어었(longer -였-). e.g. 재밌었겠네요, 모였겠네요, 알았겠습니까? I(C) '-옵-' is used to show respect toward the hearer(the other person hearing), this is common in literary style as prayer, history drama than colloquial. Though '-옵-' is rare except for the the comedy material in spoken Korean, '-옵-' shows wide usage in written Korean. '-옵-' appears before the consonant ending, e.g. 가옵고, 가옵더니. '-오' appears before the vowel ending or the ending that requires euphony, e.g. 가