Indoor vs. Indoors — What's the Difference?

"Indoor" is used to modify nouns and describe things that are situated within or designed for use inside buildings, such as indoor plants or indoor swimming pools. This term highlights the nature or purpose of an object or activity as being intended for or occurring within an enclosed space. On the other hand, "indoors" is primarily used to indicate the location or movement of someone or something going into or being inside a building. It acts as an adverb, modifying verbs, to convey actions taking place within an indoor environment, such as staying indoors during a storm.

The use of "indoor" is to attribute characteristics or specify the setting of activities and objects, emphasizing that they belong, occur, or are used inside. For example, indoor games or indoor lighting fixtures are intended for or situated within an indoor setting. Whereas "indoors" serves to describe the action or state of being inside, often used in instructions or descriptions of activities, such as moving a party indoors due to rain.

"Indoor" can be part of compound nouns or adjectives, creating terms like "indoor sports," which refers to sports designed to be played inside buildings. "Indoors," however, is used in contexts that discuss the preference, requirement, or condition of being inside, such as choosing to dine indoors rather than outside.

While "indoor" is concerned with qualifying the nature of objects, spaces, or activities as being inside, "indoors" focuses on the placement or action of being inside. This distinction is important in understanding when to use one over the other based on whether the need is to describe a characteristic (indoor) or an action/location (indoors).

Despite these differences, both "indoor" and "indoors" share the common theme of relating to or involving spaces within buildings or structures, contrasting with outdoor or outdoors activities and locations that are situated or taking place outside.