Editorial note — Front matter
Reading edition
A clause is a group of words including a verb, which is dependent upon or subordinate to a main verb or sentence, as "—that he came," "—when he went," "—that he is good," etc.
In English the subordinating conjunction may sometimes be omitted, either "I think that he is good," or "I think he is good," being usually permissible. But in Esperanto there is no variation, and the conjunction ke is never omitted.