A gerund is the present participle (-ing) form of a verb when used as a noun; gerunds express the act of doing something:

Simulating the network architecture is a preliminary means to assess its latency.

Compare these examples, which use the present participle not as a noun but as part of a verb (in past progressive tense); note that this construction can sometimes leave out words but should still be paired with the appropriate tense:

• While we were simulating the network architecture, we noticed an additional source of latency.

• While simulating the network architecture, we noticed an additional source of latency.

• Simulating the network architecture, we noticed an additional source of latency.

• We simulated the network architecture, noticing an additional source of latency. We then adjusted . . .

This use of the participle sometimes results in dangling modifiers, so make sure that the subject really is the thing performing the action!

Infinitives—the “to” form of verbs—can also be used as nouns:

• “To err is human; to forgive, divine.” —Alexander Pope (The infinitives here are grammatical subjects.)

• My goal is to finish Chapter IV by Friday. (Here, the infinitive is a predicate nominative—the thing equivalent to your goal.)

Nominalizations are nouns that capture the concept expressed in a verb or the existence of an action; many (but not all) nominalizations have common endings like -ion, -ment, and -ence:

Recent years have seen a diminishment in the adherence of certain states to the terms of the International Convention on Bagpipe Emissions Reduction.

“Diminishment” is the noun form of the verb “diminish”; “adherence,” of “adhere”; "convention," of "convene"; “emissions,” of “emit”; and “reduction,” of “reduce.”

Although nominalizations are common and grammatically valid, they can obstruct clarity if not used carefully; see the nominalizations section of our “Clarity” page for details.