Letterlike Symbols

The Letterlike Symbols block (U+2100--U+214F) contains 80 characters that look like letters but function as independent symbols. These are not mere font variants of ordinary letters -- they are distinct Unicode characters with specific meanings in mathematics, science, commerce, and typography. From the trademark sign ™ to the Planck constant symbol, from the Celsius indicator ℃ to the set of real numbers symbol, this guide catalogs every letterlike symbol in Unicode and explains when and why to use them instead of regular letters.

What Makes a Symbol "Letterlike"?

A letterlike symbol is a character that:

1. Derives visually from one or more letters (Latin, Greek, or Hebrew)
2. Has a specialized meaning distinct from the letter(s) it resembles
3. Cannot be decomposed into its component letters without losing that meaning

For example, ™ (U+2122, TRADE MARK SIGN) looks like a superscript "TM" but is a single character with a specific legal and commercial meaning. The symbol ℃ (U+2103, DEGREE CELSIUS) looks like a degree sign followed by a capital C, but it is encoded as one character because it represents a specific unit of measurement.

Complete Letterlike Symbols Reference

Commercial and Legal Symbols

The trademark ™ and service mark ℠ are among the most commonly used letterlike symbols. Note that the registered trademark sign ® (U+00AE) lives in the Latin-1 Supplement block, not in Letterlike Symbols, because it was inherited from ISO 8859-1.

Temperature and Measurement

These precomposed temperature symbols exist for compatibility with East Asian character sets (particularly CJK standards) where they were encoded as single characters. The Unicode Consortium recommends using the decomposed form (U+00B0 DEGREE SIGN + the letter) in new text, but the precomposed forms remain valid and widely used.

# Both representations are correct
celsius_precomposed = "\u2103"      # ℃ (single character)
celsius_decomposed = "\u00B0C"      # °C (degree sign + C)

# They look identical but are different strings
print(celsius_precomposed == celsius_decomposed)  # False
print(len(celsius_precomposed))  # 1
print(len(celsius_decomposed))   # 2

Number and Reference Symbols

The numero sign № is standard in Russian, German, and many European languages as an abbreviation for "number." It is commonly used where English would write "No." or "#".

Mathematical Number Set Symbols

These "double-struck" (also called "blackboard bold") characters are among the most important letterlike symbols in mathematics. In handwriting, mathematicians draw a double vertical stroke through capital letters to distinguish them from ordinary variables. The Unicode characters encode this convention as distinct code points.

Physics Constants and Symbols

The Planck constant ℎ (U+210E) and reduced Planck constant ℏ (U+210F) are fundamental in quantum mechanics. Note that the angstrom sign Å (U+212B) is canonically equivalent to the Latin capital letter A with ring above (U+00C5) -- they are treated as the same character under Unicode normalization.

Script Letter Symbols

These script and black-letter (Fraktur) variants carry specific mathematical meanings. The black-letter I (ℑ) for imaginary part and black-letter R (ℜ) for real part of a complex number are standard notation in engineering and physics.

Information and Telephony

The information symbol ℹ (U+2139) often renders as an emoji on modern platforms when followed by U+FE0F (variation selector).

Turned and Rotated Letters

The Hebrew-derived symbols ℵ (aleph), ℶ (bet), ℷ (gimel), and ℸ (dalet) are used in set theory to denote transfinite cardinal numbers. ℵ₀ (aleph-null) represents the cardinality of the natural numbers -- the smallest infinity.

Letterlike Symbols vs. Regular Letters

A common source of confusion: should you use ℃ or just type degree-C? Should you use ℕ or bold N?

Normalization Caveat

Some letterlike symbols have canonical decompositions under Unicode normalization:

import unicodedata

# Angstrom sign decomposes to A + combining ring above
angstrom = "\u212B"
normalized = unicodedata.normalize("NFC", angstrom)
print(f"Original: U+{ord(angstrom):04X}")
print(f"NFC:      U+{ord(normalized):04X}")
# Original: U+212B
# NFC:      U+00C5  (Latin Capital Letter A with Ring Above)

This means that after NFC normalization, the dedicated Angstrom sign becomes indistinguishable from the Swedish letter. Similarly, the Kelvin sign (U+212A) normalizes to ordinary K (U+004B). Applications that perform string comparison should always normalize first.

Using Letterlike Symbols in Code

HTML Entities

<p>Temperature: 20&#x2103; (68&#x2104;)</p>
<p>Product&#x2122; is a registered brand</p>
<p>Invoice &#x2116; 2024-001</p>
<p>&#x2115; &#x2282; &#x2124; &#x2282; &#x211A; &#x2282; &#x211D; &#x2282; &#x2102;</p>

Python

# Math number sets
SETS = {
    "naturals": "\u2115",  # N
    "integers": "\u2124",  # Z
    "rationals": "\u211A", # Q
    "reals": "\u211D",     # R
    "complex": "\u2102",   # C
}

# Display the number set hierarchy
chain = " \u2282 ".join(SETS.values())
print(chain)
# ℕ ⊂ ℤ ⊂ ℚ ⊂ ℝ ⊂ ℂ

JavaScript

// Temperature conversion display
function formatTemp(celsius) {
    const f = celsius * 9 / 5 + 32;
    return `${celsius}\u2103 = ${f.toFixed(1)}\u2104`;
}

console.log(formatTemp(100));
// 100℃ = 212.0℉

Font Support

For web projects needing guaranteed rendering of mathematical letterlike symbols, include a math-capable web font like STIX Two Math or Latin Modern Math.

The Letterlike Symbols block is a compact but essential collection of characters that bridge the gap between ordinary letters and specialized notation. These 80 characters serve mathematicians, scientists, lawyers, typographers, and everyday users who need precise symbolic representation that a plain letter simply cannot provide.