The comma is used to separate individual parts in complex-compound sentences, lists, isolated parts of sentences, etc. Its use in Czech is different from English. Subordinate (dependent) clauses must be always separated from their principal (independent) clauses, for instance. A comma is not placed before "a" (and), "i" (as well as), "ani" (nor) and "nebo" (or) when they connect parts of sentences or clauses in copulative conjunctions (on a same level). It must be placed in non-copulative conjunctions (consequence, emphasis, exclusion, etc.). A comma can, however, occur in front of the word "a" (and) if the former is part of comma-delimited parenthesis: "Jakub, můj mladší bratr, a jeho učitel Filip byli příliš zabráni do rozhovoru. Probírali látku, která bude u zkoušky, a též, kdo na ní bude." A comma also separates subordinate conjunctions introduced by compostide conjunctions "a proto" (and therefore) and "a tak" (and so).