Proper Noun

The one category of word that every capitalization rule — sentence case, title case, any style guide — agrees should be capitalized no matter what.

What it is

A proper noun is the specific name of a particular person, place, organization, or thing — London, Maria, GraphQL, the United Nations — as opposed to a common noun that names a general category (city, person, database, group). Proper nouns are capitalized in English regardless of where they fall in a sentence or title, which makes them the one consistent exception every capitalization rule has to account for.

Why capitalization rules can't just be mechanical

Sentence case lowercases everything except the first word and proper nouns. Title case lowercases short articles and prepositions — but only when they're functioning as articles and prepositions, never when they're part of a proper noun. This means a genuinely correct case converter can't just apply a length-based or position-based rule to every word; it has to know, in some sense, which words are names. That's what a proper-noun dictionary is for.

The modern branding problem

A second, newer complication: a growing number of real proper nouns don't follow standard English capitalization at all — iPhone, eBay, GraphQL, PostgreSQL, YouTube. A mechanical converter that title-cases or sentence-cases blindly will "fix" these into Iphone or Graphql, which is wrong — it's correcting a capitalization pattern that was never a mistake to begin with. Recognizing these specific exceptions requires an actual lookup, not a rule.

How this site handles it

The conversion engine ships with a built-in dictionary of more than 5,000 proper nouns and brand names with known non-standard capitalization, checked before any general capitalization rule is applied — so graphql in your input reliably becomes GraphQL in the output, not Graphql. Explain mode shows exactly when a word was capitalized because it matched a dictionary entry rather than a general rule. For a name the dictionary doesn't already know, custom terms let you add your own override that takes precedence from then on.

Source

Merriam-Webster — "proper noun".

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