* Convert to standard form: 2.1 thousand is the same as 2,100.

* Move the decimal: Move the decimal point to the left until you have a number between 1 and 10. You'll move it three places to the left: 2.100 becomes 2.1.

* Exponent: Since you moved the decimal three places to the left, the exponent of 10 will be +3.

* Combine: This gives you 2.1 x 10³

Therefore, 2.1 thousand in scientific notation is 2.1 x 10³