This is a very difficult question to answer for a couple of reasons:
First, we need to define what we mean by an "English" word?
English is originally a Germanic language but as a result of the Norman Conquest, thousands of French words entered the English language
Then during the industrial revolution English borrow heavily from Greek and Latin for all those chemicals and other scientific entities.
And more recently as a result of globalization more words from all over the world enter the English language.
What counts as English?
It is hard to say
Another problem is that it is hard to decide what counts as an English "word"
Is BOW 1 word or 2, or 3, or 4?
B-O-W pronounced BAU means Bend
Bow out = leave a job
B-O-W pronounced BOU means Knot as well as Weapon
Is that 4 words?
Do we count the plural Bows as a separate word?
Is that different from the third person Bows?
How about the past tense Bowed, or the gerund Bowing?
- According to Google there are over 1 million words in the English language ...
- Collins Dictionary with more than 722,000 words, meanings and phrases.
- Webster's Third New International Dictionary, Unabridged, together with its 1993 Addenda Section, includes some 470,000 entries.
- Longman Dictionary of Contemporary English 6th Edition includes 230,000 words, phrases, and meanings.
- The Second Edition of the 20-volume Oxford English Dictionary contains full entries for 171,476 words in current use, and 47,156 obsolete words.
- Cambridge Dictionary 4th Edition has over 140,000 words, phrases, meanings and examples.
How many words in the English language?
Lots of words!
A better question might be: How many words does your average native speaker know?
- According to the Economist it ranges from 20,000 to 35,000 words.
A better question still is how many words do native speakers actually use?
- According to Oxford dictionary: 7,000 words account for 90% of the language.
Most native speakers know on average about 27,000 words, but 90% of the time, native speakers of English use just 7,000 words in speech and writing.
27,000 vs 7,000 is a considerable difference.
It’s Passive vs Active vocabulary
But those numbers are for native speakers, how about non-native speakers?
How many words do we, non-native speakers, really need to know?