Regex Editor & Tester

This regex captures definitional sentences in encyclopedia style: a subject made of word/whitespace/digit characters, a linking verb phrase ("is the", "is a", "are the", "are a", or "was"), and a descriptive predicate allowing brackets, parentheses, commas, and apostrophes. It's ideal for extracting the opening definition lines of Wikipedia articles (e.g., "Paris is the capital of France") for knowledge base building or NLP definition-extraction pipelines.