data

Although data is the plural of Latin datum, it is commonly used in English as singular.

In formal academic language, however, data is still often plural:

The data are inconclusive.

criteria

Criteria is the plural of criterion:

Singular

The sole criterion in the selection process was …

Plural

Many criteria were used in the selection process.

phenomena

Phenomena is the plural of phenomenon:

Singular

This phenomenon can be seen in …

Plural

Several different phenomena can be observed …

media

Media is the plural of medium:

Singular

The internet is a new and exciting medium.

Plural

The media are often blamed for society’s ills.

bacteria

Bacteria is the plural of bacterium:

Singular

A single bacterium is too small to be seen with the naked eye.

Plural

While some bacteria are harmful, others are beneficial.

strata

Strata is the plural of stratum:

Singular

Each stratum represents a different period.

Plural

Sequences of sedimentary strata