Gerunds are nouns built from a verb with an '-ing' suffix. They can be used as the subject of a sentence, an object, or an object of preposition. They can also be used to complement a subject. Often, gerunds exist side-by-side with nouns that come from the same root but the gerund and the common noun have different shades of meaning. Examples: breath and breathing, knowledge and knowing.

Examples of gerunds as the subject of a sentence are:

• Backpacking is a rewarding pastime.
• Stretching can loosen up muscles.
• No smoking. (I.e., no smoking is allowed / you may not smoke here.)

As an object:

• We all love to go bowling on the weekend.
• He loves eating chips.

An object of preposition:

• They complained of hearing strange sounds from the next cabin.
• They sang about being eaten by bears to allay their fears.

And as a complement to a subject:

• One of the most dangerous things to do on the lake is ice-skating.