Courts apply canons of construction to interpret ambiguous language in statutes and constitutional provisions. Legal scholars divide these principles into semantic canons, which focus on grammar and legislative drafting rules, and substantive canons, which presume certain outcomes Congress would or would not want. The semantic canon noscitur a sociis, meaning 'it is known by its associates,' instructs judges to interpret words based on surrounding terms. One substantive canon directs courts to choose interpretations avoiding constitutional problems. The rule of lenity requires courts to resolve ambiguity in criminal statutes in defendants' favor, protecting due process by ensuring fair warning. No canon is absolute, as conflicting principles may point in different directions. Scholars debate whether canons genuinely constrain judges or simply give them more tools to justify predetermined results—since judges can often choose between competing canons that lead to opposite conclusions, the doctrine can obscure rather than reduce judicial discretion. Courts use these interpretive tools when statutory language proves unclear or contains multiple possible meanings.