- Nowadays is the only correct spelling of this word.
- Spelling the word as three words—now a days—is incorrect.
Nowadays means “at the present time.” It’s easy to use, but the spelling gives some people trouble.
How to Spell Nowadays
There’s only one way to spell nowadays—as one word. Even though this adverb evolved from the Middle English now adays, spelling it as more than one word today is a mistake. You shouldn’t write it as now a days, nowdays, nowaday, or any other spelling:
How to Use Nowadays in a Sentence
Nowadays should never be used as an adjective—you can’t say that your car is a nowadays car. When you start your sentence with nowadays, you should set it off with a comma, as it’s an introductory element.
You should also remember that nowadays isn’t usually used to describe something temporary that happens to be occurring at the present moment. It usually refers to something that has become common in the times we are referring to.
from Grammarly Blog https://www.grammarly.com/blog/nowadays-or-now-days/