Best answer
Both words mean lonesome or lonely in Japanese. Usually they should be 사비 시이 “sabishi-i”or 사비 시이 “samishi-i. “Notice double”i “in the end of the words.
One exception is making 하이쿠”Haiku; “seventeen-syllable short poem. in Haiku, you can use 외로움 or 외로움.
Both 외로움 “sabishi”and 외로움 “samishi”are stem of adjectives. You have to conjugate them as follows :
· present tense-positive 섭섭 “sabishi-i”
· present tense-negative 섭섭하지 “sabishi-kunai”
· past tense-positive 외로웠 “sabishi-katta”
· past tense-negative 외롭지 않았다 “sabishi-kunakatta “
Actually there are two kinds of adjectives in Japanese language.
1) [i] adjectives which ends with “i”such as 빨간색 “akai” red 흰색 “shiroi” white 새로운 시이 “atarashii” new 이전 “furui” old 달콤한 “amai” sweet 매운 “karai” salty 높은 “takai” high 낮은 “hikui” low etc.
2) [na] adjectives which consists of a noun + “na” such as 건강한 “genki-na”healthy 안전 마라 “anzen-na” safe 간단한 “kantan-na” simple 행복 마라 “kohfuku-na” happy 정직한 “shohjiki-na” honest etc