First stop  – the Oxford Concise English Dictionary 1976 edition that I used at school, with my thoughts in [square brackets]

1) Index finger – forefinger – used for pointing [I like this use of the word index because a book index shows you what is in a book and what is important]

2) (On instrument) – pointer showing value of quantity or position on scale etc  [a book index doesn’t assign value to information, but it does pick out the important information]

3) Index number – quantity indicating relative level of prices or wages at a particular date compared with that at a date taken as standard. [This is one definition that has found a lot of new uses in recent years – Global Peace Index, Social Progress Index, and Human Development Index just three among many.]

4) Number expressing physical property etc in terms of a standard (refractive index)

5) Guiding principle; thing pointing to a conclusion [again a useful thing to bear in mind about book indexes, picking out the important things and showing where they are]

6) Alphabetical list, usu. at end of book, and verb to make the index [The OED gives 1578 as the earliest use in this sense]

7) Historical use – list of books forbidden to Roman Catholics, or to be read by them only in expurgated editions. [This was new to me when I looked today so I took a deeper look – this dates from the Council of Trent in the mid 16th century and continued until the last publication in 1948 and was abolished in 1966. So a defunct use of the word and you can take a look at the list of books and authors here.]

8) Typographical – Hand shaped symbol used to draw attention to note etc

9) Mathematical – Exponent

Second stop – OED online to look at new uses of the word index that weren’t included in the 1976 published dictionary

Computing. A set of items each of which specifies one of the records of a file and contains information about its address (first found in 1962 but not relevant enough for the 1976 school dictionary)

index-link   v.  [as a back-formation] (trans.) to make dependent on such an index (i.e wages and pensions – index-linked was first recorded from 1970)

index plate – car number plate (another 1970s term that I don’t think we use these days)

So the language continues to evolve – I wonder what uses the word might be put to in future?