Stimulli

Stimulli is a nonstandard or rarely encountered term that some writers may use as the plural of stimulus. It is not a recognized or widely accepted form in English scientific or scholarly usage. The conventional plural of stimulus in English is stimulI, with the singular stimulus and the plural stimuli. In Latin, which often informs English scientific vocabulary, the noun stimulus has the standard plural stimuli, not stimulli, and stimulli does not appear in standard Latin declension tables. Consequently, stimulli is generally considered incorrect or at least nonstandard outside of specific, clearly defined contexts.

When encountered, stimulli is typically the result of misapplication of Latin plural formation rules or a deliberate neologism within a particular text. Some authors may employ it playfully or as a fictional device, but such usage should be explicitly defined to avoid confusion. In formal writing, especially in biology, psychology, or related fields, the safe practice is to use stimulus for the singular and stimuli for the plural.

Summary: stimulli is not part of standard scientific vocabulary. For clarity and accuracy, treat it as nonstandard and prefer stimulus and stimuli, or provide a clear definition if the term is introduced in a specialized or fictional context. See also stimulus, stimuli, Latin plurals, and neologisms.