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Irregular plural forms in nouns

These are mainly nouns of the Ancient Latin and Greel origin

Type	Singular	Plural	Origin	Examples in Use
Latin: -us → -i	alumnus	alumni	Latin	He is a respected alumnus of Harvard.
	radius	radii		The radii of the circle are equal.
Latin: -um → -a	curriculum	curricula	Latin	The school offers varied curricula.
	datum	data		All data have been analyzed.
Latin: -a → -ae	formula	formulae / formulas	Latin	The formulae were derived from theory.
Greek: -is → -es	analysis	analyses	Greek	Her analyses were spot on.
	crisis	crises		Several crises emerged simultaneously.
Latin: -ex/-ix → -ices	index	indices / indexes	Latin	The book has two useful indexes.
	appendix	appendices		Read the appendices for details.
Greek: -on → -a	phenomenon	phenomena	Greek	These are rare phenomena.
	criterion	criteria		Each criterion must be met.
Pluralia Tantum	—	scissors	English/Latin	The scissors are sharp.
	—	clothes		All her clothes were new.
	—	cattle		The cattle are grazing.
Singularia Tantum	news	—	English	The news is shocking.
	furniture	—		The furniture needs dusting.
	luggage	—		Her luggage was lost.