teenage是形容詞，意思是青少年的，十幾歲的。
而teenager是名詞，意思是青少年。
例句辨析：
teenage
1、Almost one in four teenage girls now smoke.
如今，十幾歲的女孩幾乎4個當中就有1個抽菸。
2、Their families had feuded since their teenage daughters quarrelled two years ago.
自從兩家十幾歲的女兒兩年前吵了一架，兩家人就結下了仇。
3、She has a teenage daughter from a previous marriage.
她前一段婚姻有一個十幾歲的女兒。
teenager
1、As a teenager he attended Tulse Hill Senior High School.
十幾歲時，他上了塔爾斯山高中。
2、She was a child prodigy, giving concerts before she was a teenager.
她是個神童，十來歲不到就舉辦音樂會了。
3、As a teenager she formed a strong attachment to one of her teachers.
少女時代的她曾迷上了自己的一個老師。
teenage是形容詞，意思是青少年的，十幾歲的。
而teenager是名詞，意思是青少年。
例句辨析：
teenage
1、Almost one in four teenage girls now smoke.
如今，十幾歲的女孩幾乎4個當中就有1個抽菸。
2、Their families had feuded since their teenage daughters quarrelled two years ago.
自從兩家十幾歲的女兒兩年前吵了一架，兩家人就結下了仇。
3、She has a teenage daughter from a previous marriage.
她前一段婚姻有一個十幾歲的女兒。
teenager
1、As a teenager he attended Tulse Hill Senior High School.
十幾歲時，他上了塔爾斯山高中。
2、She was a child prodigy, giving concerts before she was a teenager.
她是個神童，十來歲不到就舉辦音樂會了。
3、As a teenager she formed a strong attachment to one of her teachers.
少女時代的她曾迷上了自己的一個老師。