[c.] An adverbial clause which precedes a main clause is usually set off by a comma.
When long:
- Right: While I have much confidence in his sincerity, I cannot approve his decision. [The comma marks the meeting point of clauses too long to be easily read together. Brief clauses do not require the comma. Right: Where thou goest I will go.]
When ending in words that link themselves with words in the main clause:
- Right: If Jacob finds time to plow, the garden can be planted tomorrow. [The comma prevents plow the garden from being read as verb and object.]
When not closely connected with the main clause in meaning:
- Right: Although they were few, they were resolute. [Here the comma reveals the distinctness of the two stages of thought. In the sentence If it freezes the skating will be good the distinctness of the two thoughts is less emphatic, and the comma may be omitted.]
[Note.]—The comma is usually omitted when the adverbial clause follows the main clause.
- Right: The score stood twelve to twelve when the first half ended. [The adverbial clause is linked closely with the element it modifies, the predicate; punctuation is unnecessary. If the when clause were placed before the element it does not modify, the subject, a comma should be inserted.]
[d.] Restrictive clauses should not be set off by commas; non-restrictive clauses should be set off by commas. (A restrictive clause is one inseparably connected with the noun or pronoun it modifies; to omit it would change the thought of the main clause. A non-restrictive clause is less vitally connected with the noun or pronoun; to omit it would not affect the thought of the main clause.)