Names of sciences ending in ics, are generally regarded as singular. “Acoustics is a very considerable branch of physics.” Do not say, “The acoustics of this hall are good,” but “The acoustic properties of this hall are good.”
Dialectics, dynamics, economics, mathematics, ethics, politics, tactics, when used as substantives, require a verb in the singular.
Analysis
Many words like analysis, crisis, ellipsis, emphasis, hypothesis, oasis, parenthesis, synopsis, form their plurals by changing the termination is into es; as, analyses, crises, etc. The word iris takes the English plural irises; Latin plural is irides. Chrysalis has only the Latin plural, chrysalides; but chrysalid, which means the same as chrysalis, takes the English plural, chrysalids.
Terminus
Terminus, radius, alumnus, and some other words ending in us, form their plurals by changing the termination us into i; as termini, radii, etc.
Many words ending in us that formerly were written with only the Latin plural, are now given an English plural also; as, focuses, foci; cactuses, cacti; sarcophaguses, sarcophagi; convolvuluses, convolvuli ; funguses, fungi; nucleuses, nuclei.
Isthmus, prospectus, rebus, take only the English plural.
Apparatus has no plural. Avoid apparatuses.