Explanation

• Custom (singular) = habit or tradition.
• Customs (plural) = duties/taxes on goods or also official border control department.
• The meaning changes completely in plural form.

Last verified on 11-06-2026

Explanation

All three nouns change their pronunciation in plural form:

• House → Houses (/haʊs/ → /ˈhaʊzɪz/)
• Bath → Baths (/bɑːθ/ → /bɑːðz/ in many accents)
• Mouth → Mouths (/maʊθ/ → /maʊðz/)

The final sound changes (s → z or θ → ð) in pronunciation when pluralized.

Last verified on 11-06-2026

Explanation

• Curriculum is a Latin word.
• Its correct plural form is Curricula.
• Example: Different universities have different curricula.

Last verified on 11-06-2026

Explanation

• The correct plural of Appendix is Appendices.
• It follows Latin plural form rules.
• Example: The book has two appendices at the end.

Last verified on 11-06-2026

Explanation

• Radius is a singular noun; its traditional Latin plural is radii.
• In mathematics and geometry, radii is the standard plural form.
• Example: The radii of the circles were measured accurately.

Last verified on 06-06-2026