I know we inherit our alphabets (including its ordering) from the Romans, and if we trace it further we will end up with the Phoenicians or some other civilizations in the ancient Middle East. Do (or did) the alphabet sequence have any meaning/sense in it? For example, does it follow some rules based on the letter's phonology, etc. How were the positions of the additional letters determined, do they follow the same conventions/rules?
The original alphabet
We do not appear to have any ancient authority on why alphabetical order is the way it is.
Several modern scholars, such as Cyrus Gordon and Alessandro Bausani, have posited that the order is in various ways based on the calendar or the lunar zodiac. (Giovanni Garbini gives a summary of Bausani's theory in his essay The Question of the Alphabet; this is quoted in many places online.)
Scholars have been trying for centuries to explain the order of the letters of the alphabet, and no plausible answer has ever been found.
As for additional letters, there is no hard and fast rule that I'm aware of, but I believe the most common practice has been simply to add them to the end of the alphabet.
The Greeks did this with most of their new letters; beyond tau (the last letter of the Phoenician alphabet) are added upsilon, phi, chi, psi, and omega. When the Romans invented the letter G, they put it in the gap that had been created by dropping Z from its original place between F and H. However when they borrowed Y and Z from Greek later, these new letters went to the end of the line.
If the new letter is derived from an existing letter, it may sometimes be added to the alphabet immediately after it (thus J follows I, V and W follow U, Ñ follows N), but even in these cases this does not always happen; for example, the letters æ, ø, å, ä, and ö used in Scandinavian languages are added to the end of the alphabet.
Although the reason may be unknown, the Phoenician alphabet has enough phonetic patterns to support the idea that alphabetic order was at least partly influenced by phonetics. (That is, it would be unlikely for a phonetically-independent order to show this many phonetic patterns.) Some of these patterns are still observable in modern alphabets.
- the nasals are grouped together (m,n)
- (moreover, 3 of the 4 liquids are grouped together (l,m,n, though not r))
- all 3 voiced stops are grouped together (b,g,d)
- 3 of the 5 voiceless stops are near each other (p,_,q,_,_,t, though not k or ṭ)
- the sequence p,_,q,_,_,t has the same place order as b,g,d (labial, velar, dental)
The oldest known form of the North Semitic alphabet is the Ugaritic alphabet. The order of the letters is:
ʾa b g ḫ d h w z ḥ ṭ y k š l m ḏ n ẓ s ʿ p ṣ q r ṯ ġ t ʾi ʾu s2
As you can see, the voiced stops b g d and the liquids/nasals l m n are NOT grouped together without a break. There is no perceptible logic to this order.
it is interesting to list the letters in this way:
A b c d
E f g h
I j k l m n
O p q r s t
U v w x y z
this is slightly more ordered than we should expect from pure chance. it does not work as well if we do it in a more early-Roman way:
A b c d
E f h
I k l m n
O p q r s t
just mentioning this here because i believe it may be interesting. if anything, the alphabet has grown a tad more orderly over time through the addition of new letters and their respective placements.
I find a reason for the ordering of sequence in English alphabet system.
For instance take U and V. Transformation of (letter no. 21) U-shaped curve (flat, scattered below) to (letter no. 22) V-shaped curve (steep) in many economic, social, and behavioral cycles is gradual, process demanding consistency (unity of effort) so that downward curvature polishes to a point after iteration meaning operation accomplished or victory achieved. From shape perspective, V is then improvement, perfection of U.
Chances are that most will not agree with my line of thinking. As a result, I am not posting here any more of my observation but would love to do so if there is any word of support.