Nouns of Foreign Origin in English

In English there is a group of nouns with very unusual plural forms. This group consists mainly of nouns of foreign origin especially of Latin and Greek. Below you can find a list with some examples of such nouns.

Singular Plural
analysis analyses
antenna antennae / antennas
appendix appendixes/appendices
axis axes
bacterium bacteria
basis bases
bureau bureaux
cactus cactuses/cacti
codex codices
criterion criteria
crisis crises
curriculum curricula
datum data
diagnosis diagnoses
focus focuses/foci
formula formulae / formulas
fungus fungi
index indexes/indices
kibbutz kibbutzim
larva larvae
medium mediums/media
nucleus nuclei
oasis oases
octopus octopuses/octopi
phenomenon phenomena
stimulus stimuli
syllabus syllabuses/syllabi
tempo tempi
terminus termini / terminuses
thesis theses