Yes, 생활 is an ordinary noun which can be used by itself. 인생, 삶, and 생활 are all related to "life" and "living", but have different connotations. 인생 refers to life as a whole emphasizing the process and entirety of it, and thus sounds more serious. 생활 means the various details of day-to-day life, including finance and livelihood ("이 돈으로 어떻게 한 달을 생활해?"). 삶 is sort of in between, and can be used like 인생 or 생활 (나의 인생 = 나의 삶, 생활에 쪼들리다 = 삶에 쪼들리다). So 삶 and 생활, or 인생 and 삶 are often interchangeable, but 인생 and 생활 are usually not. - 인생[삶]은 때론 달콤하기도, 때론 쓰디쓰기도 하다: Life is sweet sometimes, bitter at other times. - 그의 생활[삶]은 나날이 궁핍해져 갔다: His days only got more destitute with the passing time. - "삶이 그대를 속일지라도", "생활이 그대를 속일지라도" - A Pushkin poem, "Should This Life Sometime Deceive You".