The Editor’s Manual
Free learning resource on English grammar, punctuation, usage, and style.
How words and phrases are used: formal, acceptable, and incorrect usage.
Data can be a plural noun (“the data are”) or a singular mass noun (“the data is”). As a mass noun, it is used much like the word “information.”
Contractions are shortened forms in which some letters or sounds are omitted. An apostrophe marks the omission. Avoid using contractions in formal texts.
Use “who” for the subject and “whom” for the object in a sentence. In everyday communication, “who” can replace “whom.” To choose between “who” and “whom,” a simple trick is to form a question and frame its answer.
Split infinitives are grammatically fine in English. Splitting an infinitive can help clarify meaning and emphasize the right word (e.g., “I promise to always be there for you”).
The word “effect” is used most often as a noun, and “affect” most often as a verb: when you affect something, you have an effect on it.