A more thorough explanation:

Definition: Plain meaning refers to the sense of anything, especially words, that is conveyed or intended to be conveyed by a written or oral statement or other communicative act. It includes a mistaken but reasonable understanding of a communication and is often held to its objective meaning, which is considered to have had reason to know, even if the party subjectively understood or intended something else. Plain meaning is attributed to a document by giving the words their ordinary sense, without referring to extrinsic indications of the author's intent.

• If a contract states that a payment is due on the 1st of the month, the plain meaning is that the payment is due on the first day of each month.
• If a law states that it is illegal to "drive a vehicle on a sidewalk," the plain meaning is that it is illegal to operate a vehicle on a pedestrian walkway.

These examples illustrate how plain meaning is determined by the ordinary sense of the words used in a document or communication, without considering any additional context or intent. Even if a party subjectively understood or intended something else, the plain meaning of the words used will be held to its objective meaning.