Wh-words: how, what, when, where, which, who, whom, whose, why

　Wh-ever words: however, whatever, whenever, wherever, whichever, whoever, whomever

2. Except for that, noun clause markers cannot be omitted. Only that can be omitted, but it cannot be omitted if it is used in a subject and appositive clause.

correct:

Billy's friends didn't know that he couldn't swim.

correct:

Billy's friends didn't know he couldn't swim.

correct:

Billy's mistake was that he refused to take lessons.

correct:

Billy's mistake was he refused to take lessons.

correct:

That Billy jumped off the pier surprised everyone.

not correct:

* Billy jumped off the pier surprised everyone.

3. Remember! Use statement word order in wh- and if-whether noun clauses.

* Do you know what time is it? (Question word order: is it)

correct:

Do you know what time it is? (Statement word order: it is)

not correct:

* Everybody wondered where did Billy go. (Question word order: did Billy go)

correct:

Everybody wondered where Billy went. (Statement word order: Billy went)

4. Sequence of tenses in sentences containing noun clauses:

When the main verb (the verb in the independent clause) is present, the verb in the noun clause can be in different tenses.

When the main verb (the verb in the independent clause) is past, the verb in the noun clause is