Nowadays (注意這個字的拼法，不是 nowdays)、these days 和 today 都可用作副詞來表示相較於過去的「現今，當今，如今」。例如：
- Most people think kids nowadays are lazy. (大多數人都認為現在的小孩很懶)
- People nowadays live far more comfortable lives. (現今人們過著比過去舒適很多的生活)
These days 比較不正式一些。例如：
- Young people these days don’t respect their teachers any more. (時下的年輕人不再尊敬他們的老師)
- These days you seldom see a young person give up their seat for an older person on the bus. (現今在公車上你很少會見到年輕人讓位給年長者)
Today 略微正式一點。例如：
- People today are much more concerned about their health than they were in the past. (現在人們比以前更關心自己的健康)
- Computers today are so advanced. (現在的電腦很先進)
= The computers of today are so advanced.
Today 還可當名詞用，而且可使用所有格 ‘s 或 of today 結構。這是一項相當正式的用法，但 nowadays 或 these days 則無此用法，因為它們皆不可當名詞用。再者，「today’s + 名詞」前面不能有定冠詞 the，但「名詞 + of today」前面則須有定冠詞。例如：
- In today’s rapidly changing society almost anything seems possible. (在當今變化快速的社會中，似乎任何事情都有可能發生) (正)
In nowadays’ rapidly changing society almost anything seems possible. (誤)
In these days’ rapidly changing society almost anything seems possible. (誤) - She is one of the best-known novelists of today. (她是當今最負盛名的小說家之一) (正)
She is one of the best-known novelists of nowadays. (誤)
She is one of the best-known novelists of these days. (誤)
Nowadays、these days 或 today 皆不可當形容詞用。例如：
- Teenagers nowadays/these days/today are so sophisticated. (現在的青少年太世故了) (正)
= Today’s teenagers are so sophisticated.
= The teenagers of today are so sophisticated. - The nowadays teenagers / The these days teenagers / The today teenagers are so sophisticated. (誤)