One man's indexes are another man's indices...

[DRT]

...or are they?

Wot's the diff?

[jdaw1]

If an index is a number summarising some larger set of data, I think its plural is “indices†: “The various UK retail price indices are climbing swiftly†.

If an index is a list or table pointing into a larger set of data, I think its plural is “indexes†: “Tasting notes for individual Ports, with alphabetical and date-ordered indexes of tasting notes†.

But I realised as I typed “indexes† that this neat distinction might not yet be widely accepted. (Translation: I invented it, and liked it so much that I’m now trying to encourage its use.)

[DRT]

Was it the three-quarters of a bottle of Morgan 91 or the logic in the post immediately above this one that made me laugh out loud?

[KillerB]

The rule is "be consistent". The plural of "Index" is classically "Indices", whatever its use but modern usage allows for "Indexes", especially amongst Americans and the IT industry. Just be consistent amongst yourself.#

This reminds me of my Scouse friend Mark, who thought that a book that you read was pronounced with gutteral "bucggh", whilst the verb "to book" was pronounced with a sing-song "buuk". However, he was wrong on both counts.

[JacobH]

The OED suggests both, but notes that indices is more frequently encountered during “technical use† (which may co-incidentally result in the same usage patterns as jdaw1 suggests).

Interesting that when index is used a verb, it does not have an irregular form (i.e. “he indexes† rather than “he indices†).

[jdaw1]

modern usage allows for "Indexes", especially … the IT industry

Not so far from what I was saying.

[KillerB]

The OED suggests both, but notes that indices is more frequently encountered during “technical use† (which may co-incidentally result in the same usage patterns as jdaw1 suggests).

Interesting that when index is used a verb, it does not have an irregular form (i.e. “he indexes† rather than “he indices†).

The third person present and the plural are not necessarily related.

Not so far from what I was saying.

modern usage allows for "Indexes", especially … the IT industry

Not so far from what I was saying.

You ellipsed out the American bit which is the reason why the IT industry tends to use it. I was once told that it would always be "Indexes" for IT because an American first used the term on databases. I replied that the plural of a word doesn't change just because somebody uses it somewhere else for ostensibly the same purpose as this is the same use that libraries have had for centuries: "Bucggh Indexes" and "Buuk Indices".

[jdaw1]

IT often uses plurals and past tenses containing the root (often the third-person imperative). Any postscript programmer would be happy to use the term unbinded (source shown coloured) (e.g., here), just as a database might have one index or several indexes. Standard IT word formation. This word formation might be related to typography: it allows the root word to be shown in a monospaced typeface.

[KillerB]

IT often uses plurals and past tenses containing the root (often the third-person imperative).

That doesn't make IT right. Remember: they went into IT because they couldn't spell nor understand grammar.

Alex - Maths graduate and IT professional for 21 years.

[jdaw1]

went into IT because they couldn't spell nor understand grammar.

… because they could neither spell nor understand grammar …

[JacobH]

IT often uses plurals and past tenses containing the root (often the third-person imperative).

That doesn't make IT right. Remember: they went into IT because they couldn't spell nor understand grammar.

Alex - Maths graduate and IT professional for 21 years.

Thankfully, the use of spell-checks when doing something important militates against the worse consequences of this, especially when drawing up new protocols…

[KillerB]

went into IT because they couldn't spell nor understand grammar.

… because they could neither spell nor understand grammar …

the "n't" was an abbreviation of "neither" - I made that up because I am in IT.