The alphabet does not contain only 26 letters depending on the era, lanquage, etc. The number varies greatly.
"In the year 1011, a writer named Byrhtferð ordered the Old English alphabet for numerological purposes. He listed the 24 letters of the Latin alphabet (including ampersand) first, then 5 additional English letters, starting with the Tironian nota ond, ⁊, an insular symbol for and:
...In Modern English orthography, thorn (þ), eth (Ð), wynn (Ƿ) and yogh (Ȝ) are obsolete
...The letters Þ and Ð are still used in present-day Icelandic. Wynn disappeared from English around the 14th century when it was supplanted by uu, which ultimately developed into the modern w. Yogh disappeared around the 15th century and was typically replaced by gh.
The letters u and j, as distinct from v and i, were introduced in the 16th century, and w assumed the status of an independent letter, so that the English alphabet is now considered to consist of the following 26 letters:"
"Futhorc is a runic alphabet, extended from the Elder Futhark from 24 to between 26 and 33 characters. It was used probably from the 5th century onward, recording Old English and Old Frisian."
"Latin alphabet are used by the writing systems of many languages throughout the world. The tables below summarize and compare several of those alphabets.
...In this list of 41 languages, the twelve letters used for all are A, E, G, H, I, L, M, N, O, R, S and T.
...Some languages have extended the Latin alphabet with ligatures, modified letters, or digraphs."