系, けい
Noun, used as a suffix
1. system, lineage, group
Mathematics term
2. corollary
Geology term
3. system (range of strata that correspond to a particular time period)
4. (taxonomical) series
Windows系OSではアドミニストレーターアカウントがルートに相当する。
共和国, きょうわこく
republic, commonwealth
アメリカ合衆国は共和国である。
が
Particle
1. indicates the subject of a sentence
literary in modern Japanese; usu. written as ヶ in place names
2. indicates possession
Conjunction
3. but, however, (and) yet, though, although, while
4. and
5. used after an introductory remark or explanation