Difference between <acronym> and <abbr>?

Question

Definitionally they seem the same, yet they are deemed dissimilar enough by the W3C to have separate tag definitions. What is the semantic difference between <acronym> and <abbr> in terms of linguistics, the HTML spec and interpretation.

Answer 1

An acronym is the initial letters of some words (e.g.Hypertext Mark-up Language => HTML), while an abbreviation is a shortened form of a word (e.g. abbreviation => abbr).

Wikipeida gives a more accurate view of the nitty-gritty details.

Answer 2

http://www.w3.org/TR/html401/struct/text.html#edef-ABBR says:

Western languages make extensive use of acronyms such as "GmbH", "NATO", and "F.B.I.", as well as abbreviations like "M.", "Inc.", "et al.", "etc.". Both Chinese and Japanese use analogous abbreviation mechanisms, wherein a long name is referred to subsequently with a subset of the Han characters from the original occurrence.

So I guess Aa Bb Cccccc -> ABC is acronym, -> Ab Bb Ccc. is abbreviation. Practically I saw people use <abbr>.

Answer 3

abbreviation: A shortened form of a word.
ex: lb., amt., mgmt.

initialism: An abbreviation formed from the initial letters of a phrase
ex: HTML, SVG

acronym: An initialism that is pronounced as a word.
ex: radar, scuba, JIT, WYSIWYG

Answer 4

Actually, the differences are so small that HTML5 decided to drop acronym in favour of abbr.