～っぽい
-ish / -like / tends to
～っぽい is a casual suffix that turns a noun or a verb stem into an い-adjective meaning “has the qualities of” or “tends to”.
It works like English “-ish” (childish) or “-y” (watery). Once formed, the new word conjugates like any い-adjective: 子供っぽくない, 子供っぽかった.
1. Noun + っぽい: -ish, like
Attached to a noun, っぽい says something has the look or feel of that noun, often with a slightly critical tone when describing people.
彼は子供っぽい。
“He's childish.”
- 彼（かれ）= he
- は = topic marker
- 子供っぽい（こどもっぽい）= childish
このスープは水っぽい。
“This soup is watery.”
- この = this
- スープ = soup
- は = topic marker
- 水っぽい（みずっぽい）= watery
2. Verb stem + っぽい: tends to
Attached to the ます-stem of certain verbs, っぽい describes a habitual tendency, as in 忘れっぽい (forgetful) or 飽きっぽい (quick to get bored).
父は最近、忘れっぽくなった。
“My father has become forgetful lately.”
- 父（ちち）= (my) father
- は = topic marker
- 最近（さいきん）= lately
- 忘れっぽくなった（わすれっぽくなった）= has become forgetful
Be careful to distinguish ～っぽい from ～らしい: 子供っぽい means childish in a way that does not suit the person (a criticism of an adult), while 子供らしい means childlike in exactly the way a child should be (usually positive).
How to form it
Noun / Verb ます-stem + っぽい
- 子供（こども）= child → 子供っぽい（こどもっぽい）= childish
- 水（みず）= water → 水っぽい（みずっぽい）= watery
- 忘れる（わすれる）= to forget → 忘れっぽい（わすれっぽい）= forgetful
Key idea
～っぽい paints something with the color of another word: not the real thing itself, but strongly tinted with its qualities, “-ish”, “-y”, or “prone to”.
Other N3 grammar
Updated .