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Suffix · forms adjectives

-defined

Judges how clear the boundaries or meaning of something are: well-defined (clear) versus ill-defined (vague, unclear).

In Spanish: definido / delimitado / con límites clarosLiterary

Written by Bryan López, English teacher · Updated August 2026

What this suffix does

-defined forms compound adjectives that evaluate the clarity, precision, and adequacy of definition — whether of concepts, boundaries, roles, or scope. Well-defined, ill-defined, sharply-defined, clearly-defined, loosely-defined, narrowly-defined — each compound judges how precisely something has been given its limits and meaning. In academic writing, legal drafting, and policy analysis, poorly-defined terms and ill-defined scope are among the primary sources of confusion and dispute. "Well-defined" therefore carries significant intellectual weight.

How it is formed

Adverb + defined.

  • well + defined
    well-defined (clear)
  • ill + defined
    ill-defined (vague, unclear)
  • sharply + defined
    sharply-defined (crisp, clearly marked)

This is not a productive rule you can apply freely: it is a closed set of fixed expressions. Learn them one by one as set phrases.

How it is pronounced

-defined

Tap the button to hear how the ending sounds. Each word in the table has its own audio.

Examples

Base word
With -defined
In a phrase
  • wellwell-definedThe job has well-defined responsibilities, so there's no confusion.
  • illill-definedThe rules were so ill-defined that nobody knew what to do.
  • sharplysharply-definedThe mountain's sharply-defined edge stood out against the sky.
  • looselyloosely-definedHer role at the company is loosely-defined, she does a bit of everything.
  • narrowlynarrowly-definedThe contract has a narrowly-defined scope, so extra work isn't included.

Common mistakes

well-defined = simple, straightforward, or uncomplicated
well-defined = precisely specified with clear limits, whatever its complexity

"Well-defined" describes precision of specification, not simplicity of subject. A very complex legal concept can be well-defined — precisely delimited with clear boundaries even if the subject itself is intricate. A simple concept can be ill-defined — imprecisely specified despite its apparent simplicity. The compound judges the quality of the definition, not the complexity of what is defined.

"ill-defined" = vague or unclear (only describes concepts and terms)
"ill-defined" applies to anything that needs precise limits: boundaries, roles, responsibilities, mandates, scope

"Ill-defined" can describe not just concepts and terms but physical boundaries (an ill-defined coastline), roles and responsibilities (ill-defined authority), the scope of a project or inquiry (ill-defined mandate), and any other thing whose precision of specification can be evaluated. The compound is wider than its most common use in conceptual contexts.

A trick to remember it

"Ill-defined" is one of the most powerful critical tools available in academic, legal, and policy writing — and one of the most common sources of real-world problems. An ill-defined term in a contract creates years of litigation; an ill-defined role creates perpetual territorial conflict; an ill-defined scope creates an inquiry that either misses the problem or exceeds its authority. Identifying what is ill-defined is often the first step in fixing what is wrong with a system.

Practise what you learned

Exercise 1 · Form the word

Fill in: "The ___ criteria for promotion meant that decisions could be made on any basis the manager chose." (imprecisely specified; without clear limits that would constrain interpretation)

Hint: Ill + defined = defined badly; without the precision needed to constrain interpretation or application.

Exercise 2 · Pick the right one

"The sharply-defined boundary between permitted and prohibited activity left no room for interpretation." What does "sharply-defined" tell us about the boundary?

Exercise 3 · Form the word

Fill in: "The ___ mandate allowed the commission to do what was needed without wasting resources on jurisdiction disputes." (specified with precision and clarity; with limits clear enough to guide action without ambiguity)

Hint: Well + defined = specified with adequate precision; with limits clear enough to be functional.

Frequently asked questions

What does the suffix -defined mean in English?

The suffix -defined judges how clear the boundaries or meaning of something are: well-defined (clear) versus ill-defined (vague, unclear). In Spanish it usually maps to definido / delimitado / con límites claros.

Can you give an example of a word with -defined?

"well" becomes "well-defined". It is a typical example of the -defined suffix.

Other useful suffixes

  • -founded

    Judges how solid the basis of a claim or fear is: well-founded (justified, based on good evidence) versus ill-founded (baseless).

  • -placed

    Judges how well something is positioned: well-placed (in the right spot) versus ill-placed (poorly positioned).

  • -reasoned

    Judges how solid an argument's logic is: well-reasoned (logically sound) versus poorly-reasoned (weak logic).

Learn every English suffix

-tion, -ness, -ful, -ly, -able... every ending you need to understand thousands of words at once.

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