E (minuscule: e; Polish E z ogonkiem, "E with a little tail"; Lithuanian e nosine, "e nasal") is a letter in the Polish alphabet, Lithuanian alphabet, and the Dalecarlian alphabet. In Latin, Irish, and Old Norse palaeography, it is known as E caudata (tailed E).

E e is the 9th letter in the Lithuanian alphabet, and is also used in the Colognian language of Cologne, Germany, and Cheyenne language.

The grapheme E, e (E with caron) is used in Czech, Upper Sorbian and Lower Sorbian alphabets.

E (named e , plural ees) is the fifth letter and the second vowel in the modern English alphabet and the ISO basic Latin alphabet. It is the most commonly used letter in many languages, including: Czech, Danish, Dutch, English, French, German, Hungarian, Latin, Norwegian, Spanish, and Swedish.

or can be

• The letter E with a grave accent.
• In English, the letter è is sometimes used in the past tense forms of verbs in poetic texts to indicate that the final syllable should be pronounced separately. For example, blessèd would indicate the pronunciation rather than . It also occurs in loanwords such as Italian caffè.
• In French, it always represents a sound of letter e when this is at the end of a syllable.
• È means "is" in modern Italian , e.g. il cane è piccolo meaning "the dog is small". It is derived from Latin ĕst and is accented to distinguish it from the conjunction e meaning "and". È is also used to mark a stressed at the end of a word only, as in caffè.
• È (è) is also used for an with a falling tone in pinyin, the Chinese language roman-alphabet transcription system. The word 鄂, consisting only of this vowel, is an abbreviation for the Hubei province of the People's Republic of China.
• È (è) is also used in Macedonian Latin as an equivalent of the letter ye with grave (Ѐ, ѐ).

(e-acute) is a letter of the Latin alphabet. It is found in Catalan, Czech, Danish, English, French, Galician, Hungarian, Icelandic, Irish, Italian, Kashubian, Luxembourgish, Occitan, Norwegian, Portuguese, Slovak, Spanish, Swedish, Vietnamese, and Welsh languages, as a variant of the letter "e". In English, it may be observed as a pronunciation aid in loanwords (e.g., résumé from French) or romanizations (e.g., Pokémon from Japanese). This is also used in Dutch and Navajo.

Ê is not considered a separate letter in Afrikaans, but rather a variation of the letter "e".

(e-diaeresis) is a letter in the Albanian, Kashubian and Ladin alphabets. This letter also appears in Afrikaans, Dutch, French, Abruzzese dialect (especially its version Ascolano) and Luxembourgish as a variant of letter e. The letter is used in Seneca, in Taiwanese Hokkien, in Turoyo and in Uyghur when written in Latin script.

A breve (, less often ; ; from the Latin brevis “short, brief”) is the diacritic mark ˘, shaped like the bottom half of a circle. As used in Ancient Greek, it is also called vrachy or brachy. It resembles the caron (the wedge or háček in Czech) but is rounded; the caron has a sharp tip.

[e] is Korean hip-hop group Epik High's sixth official album released in September 2009 and is also their third major album release of the same year. The two other albums released in 2009 are Map the Soul and Remixing the Human Soul, an electronica-inspired remix compilation album with labelmates Planet Shiver. Like Map the Soul before it, [e] includes a complimentary mini-book along with the actual audio CDs. The 74 page mini-book contains song lyrics, interviews, photographs, and various production notes from the artists themselves.

E is the fifth letter of the Latin alphabet.

The number is an important mathematical constant that is the base of the natural logarithm. It is approximately equal to 2.71828, and is the limit of as approaches infinity, an expression that arises in the study of compound interest. It can also be calculated as the sum of the infinite series

E! Entertainment Television, LLC (more commonly known as E! and formerly E!: Entertainment Television) is an American basic cable and satellite television channel that is owned by the NBCUniversal Cable division of NBCUniversal. It features entertainment-related programming, reality television, feature films and occasionally series and specials unrelated to the entertainment industry. As of February 2015, E! has an audience reach of approximately 94,296,000 American households (81.0% of households). The channel is also available in Canada, which broadcasts original programming at the same as the United States and localized versions across Europe, Asia and Australia.

E-Z configuration, or the E-Z convention, is the IUPAC preferred method of describing the absolute stereochemistry of double bonds in organic chemistry. It is an extension of cis/trans notation (which only describes relative stereochemistry) that can be used to describe double bonds having two, three or four substituents.

Electromotive force, also called emf (denoted and measured in volt), is the voltage developed by any source of electrical energy such as a battery or dynamo. It is generally defined as the electrical potential for a source in a circuit. A device that supplies electrical energy is called a seat of electromotive force or emf. Emfs convert chemical, mechanical, and other forms of energy into electrical energy. The product of such a device is also known as emf.

In computing and telecommunication, an escape character is a character which invokes an alternative interpretation on subsequent characters in a character sequence. An escape character is a particular case of metacharacters. Generally, the judgement of whether something is an escape character or not depends on context.

The estimated sign, e, also referred to as the e-mark, is a mark that can be found on some pre-packed goods in Europe. The estimated sign indicates that the packaging is filled according to the European Union Directive 76/211/EEC (amended by 2007/45/EC).

The Euler–Mascheroni constant (also called Euler's constant) is a mathematical constant recurring in analysis and number theory, usually denoted by the lowercase Greek letter gamma .

Indian Standard Time (IST) is the time observed throughout India and Sri Lanka, with a time offset of UTC+05:30. India does not observe daylight saving time (DST) or other seasonal adjustments. In military and aviation time IST is designated E* ("Echo-Star").

A macron is a diacritical mark, a straight bar placed above a letter, usually a vowel. Its name derives from the Greek  (makrón), meaning "long", and was originally used to mark long or heavy syllables in Greco-Roman metrics. It now more often marks a long vowel. In the International Phonetic Alphabet, the macron is used to indicate a mid-tone; the sign for a long vowel is instead a modified triangular colon .

In physics, mass–energy equivalence is a concept formulated by Albert Einstein that explains the relationship between mass and energy. It states every mass has an energy equivalent and vice versa—expressed using the formula