発音区別符号 / ダイアクリティック

What is a Diacritical Mark?

A diacritical mark (also called a diacritic) is a small sign or symbol added to a letter to modify its pronunciation, indicate stress, distinguish between words that would otherwise be spelled identically, or mark grammatical features. Diacritical marks are foundational to most writing systems that use the Latin, Greek, Cyrillic, Arabic, Hebrew, and many other scripts.

Common examples in Latin-script languages include the acute accent (é), grave accent (è), circumflex (ê), umlaut (ü), tilde (ñ), cedilla (ç), and the ring above (å). These are not decorations — they represent distinct sounds and often change the meaning of a word entirely.

Precomposed vs. Combining Forms

Unicode encodes diacritical characters in two ways:

Precomposed characters are single code points that combine a base letter and its diacritic. For example, é is U+00E9 (a single code point). These exist for compatibility with legacy encodings and convenience.

Combining characters are separate diacritical marks (U+0300–U+036F) that attach to the preceding base character. The same é can be represented as U+0065 (e) followed by U+0301 (combining acute accent).

Both representations are canonically equivalent — Unicode Normalization Form C (NFC) prefers precomposed forms, while NFD decomposes them into base + combining sequences.

Common Diacritical Marks

Typing Diacritical Marks

macOS: Hold a key to see a popover (e.g., hold e to choose é, è, ê). Or use Option key combos: Option+E then E = é.

Windows: Use Alt codes, the Character Map app, or configure a locale keyboard layout.

HTML entities:

&eacute;   <!-- é -->
&Uuml;     <!-- Ü -->
&ntilde;   <!-- ñ -->
&ccedil;   <!-- ç -->

Unicode escape:

"\u00e9"  # é in Python
"\u00fc"  # ü

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