History of English
The English language has a long and varied history which is, not unnaturally, bound up with the history of England, the British Isles and its peoples.
Number of words in English
Although you will sometimes find statements to the effect that "English has more words than any other language", the situation is by no means so clear cut.
There is the simple question of how we count "words".
How would one count conjugations? Past participles used as adjectives? Species names for flowers and insects which are common to all languages? Chemical names? (With these you can dwarf the number of "normal" words in any language.)
Then there are agglutinative languages which make up "words" on the fly by combining elements - giving rise to the alleged vast number of "words" for snow in Eskimo languages. How would you count those?
Equally difficult is the question of whether a word is actually used - it may exist but be so obsolete that it isn't used any more. Do we count it or not? Do we count slang? Do we count regional words? Do we count a word if it is used in the UK but not in the US or in all international varieties of English (including Indian English, which has a large selection of words from native languages.)
If a word has two spellings, does that count as one word or two? Or two past participles like "lighted" and "lit" or "dived" and "dove"?
One could count the words in a dictionary and do it that way - but which dictionary? English dictionaries vary wildly in the words they include. One might use, say, the OED, but a very large proportion of the words in that are simply dead.
Another solution might to try to estimate the vocabulary of the average speaker, but even this presents difficulties. Partly because we all have an active and a passive vocabulary and partly because we can often "know" words we have never seen before, either because of their context or because they are made up of other parts of words we already know.