Latin Small Letter M
Marking the midpoint of the 26-letter Latin alphabet, lowercase 'm' is the thirteenth letter and a bilabial nasal consonant that accounts for roughly 2.4 % of characters in typical English corpora. It lends its name — via the uppercase form — to the typographic 'em' unit, a widely used measurement in page layout and CSS. Its ASCII code point is 109 (0x6D), 32 above its uppercase counterpart 'M' at 77 (0x4D), maintaining the single-bit case offset (bit 5) shared by all ASCII A–Z / a–z pairs.
Technical Details
Code Example
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// main is the entry pointint main(int argc, char *argv[]) {printf("Hello, World!\n");return 0;}
Common Usage
Case-sensitive SI prefix: Lowercase 'm' denotes milli- (10⁻³) while uppercase 'M' denotes mega- (10⁶) — a nine-order-of-magnitude difference hinging on a single case distinction. This makes capitalization critically important in engineering and scientific notation (mW vs MW, mm vs Mm), and serves as a striking real-world example of case sensitivity outside software.
Typographic em unit: The 'em' — named after the letter M — is a relative unit historically associated with the width of an uppercase M in a given typeface. In CSS, 1em equals the computed font-size of the current element, making it central to responsive typography, spacing, and layout scaling. Related constructs like the em dash (—) and em space also derive from this measurement.
Regex multiline flag: In JavaScript, Python (re.MULTILINE), Perl, and PCRE, the 'm' flag changes the behavior of ^ and $ anchors so they match the start and end of each line rather than the entire string. This distinction frequently catches developers working with multi-line input, as the default single-line anchor behavior silently ignores embedded line breaks.
Diacritical variants: ṃ (dot below) is used in IAST transliteration of Sanskrit and Pali to represent the anusvara nasal sound, and ṁ (dot above) appears in some Romanization systems and historical Irish manuscript orthography. Beyond these, 'm' carries a relatively small diacritical family among Latin consonants.
Case-sensitive SI prefix: Lowercase 'm' denotes milli- (10⁻³) while uppercase 'M' denotes mega- (10⁶) — a nine-order-of-magnitude difference hinging on a single case distinction. This makes capitalization critically important in engineering and scientific notation (mW vs MW, mm vs Mm), and serves as a striking real-world example of case sensitivity outside software.
Typographic em unit: The 'em' — named after the letter M — is a relative unit historically associated with the width of an uppercase M in a given typeface. In CSS, 1em equals the computed font-size of the current element, making it central to responsive typography, spacing, and layout scaling. Related constructs like the em dash (—) and em space also derive from this measurement.
Regex multiline flag: In JavaScript, Python (re.MULTILINE), Perl, and PCRE, the 'm' flag changes the behavior of ^ and $ anchors so they match the start and end of each line rather than the entire string. This distinction frequently catches developers working with multi-line input, as the default single-line anchor behavior silently ignores embedded line breaks.
Diacritical variants: ṃ (dot below) is used in IAST transliteration of Sanskrit and Pali to represent the anusvara nasal sound, and ṁ (dot above) appears in some Romanization systems and historical Irish manuscript orthography. Beyond these, 'm' carries a relatively small diacritical family among Latin consonants.