mainly

mainly — adverb

1. used to say that something is true in most cases, or that a particular reason, f

1.adverbB1
Definition

used to say that something is true in most cases, or that a particular reason, fact, or part is the most important one

Example

The delay was mainly caused by the heavy snow on the motorway.

passive: be mainly + caused by [reason factor]

Sade chose that university mainly because of its excellent music programme.

mainly because of [noun phrase] — reason focus

Common collocations
  • mainly because
  • mainly due to
  • mainly about
  • mainly for
  • mainly concerned with
  • mainly responsible for
Synonyms
  • mostly

    Similar in meaning but 'mostly' emphasises the largest part of a group, while 'mainly' often highlights a primary reason or purpose

  • primarily

    More formal than 'mainly'; common in academic and professional writing

  • chiefly

    Slightly more formal and less frequent in everyday speech, but interchangeable in most contexts

  • largely

    Emphasises the extent or scale of something rather than singling out the most important factor

Antonyms
  • partially

    Suggests only a portion, not the majority

  • secondarily

    Indicates something of lesser importance, the opposite of what 'mainly' picks out

Grammar Patterns

mainly + verb phrase

mainly + noun phrase

mainly because of / due to + noun phrase

Usage Note

Can be placed before the main verb (e.g., 'mainly reads'), after the verb 'be' ('is mainly'), or directly before a noun phrase ('mainly fiction'). Unlike 'mostly', 'mainly' is more often used to point to a reason or purpose rather than a numerical majority.

Common Mistakes

The mainly people voted for change.
Most people voted for change.
'mainly' is an adverb and cannot modify a noun directly; use 'most' instead.

Word family

Synonym discussion

Sense: adverb/1

These adverbs all indicate that something is true to a great extent, but they differ in emphasis. 'Mainly' points to the most important reason or purpose behind something ('He moved mainly for the job'). 'Mostly' focuses on the numerical or quantitative majority — the largest part of a group or set ('The crowd was mostly students'). 'Primarily' is the most formal of the group and is typical in academic or professional contexts where precision matters ('The study focuses primarily on urban areas'). 'Largely' describes the overall size or scale of something rather than singling out a primary factor ('The project was largely successful'). 'Chiefly' is slightly old-fashioned and less common in everyday speech but still used in formal writing ('The book is chiefly concerned with 19th-century politics').

mainly ↗mostly ↗primarily ↗largely ↗chiefly

Common collocations

Nouns

  • mainly students
  • mainly women
  • mainly children
  • mainly fiction

Phrases

  • mainly because
  • mainly due to
  • mainly concerned with
  • mainly in the form of
  • mainly made up of

Prepositions

  • mainly because of
  • mainly due to
  • mainly for
  • mainly about

Etymology

Old EnglishEnglish

Formed in English by adding the suffix '-ly' to the adjective 'main'. 'Main' comes from Old English 'mægen' meaning 'strength, power, force'. The original meaning of 'mainly' was 'powerfully' or 'forcibly' (13th century), but this sense faded. By the 17th–18th centuries the word had shifted to its modern meaning of 'for the most part' or 'chiefly'.