っぽい-ish, -like, Characteristic of, Typical of, Tendency to

Both がち and っぽい describe tendencies or characteristic qualities, but differ in nuance. がち is neutral and used for tendencies that happen often, e.g. つい忘れがちだ ('I tend to forget.'). っぽい expresses an inherent quality or the appearance of something, similar to the English '~ish', e.g. 子供っぽい性格 ('a childish personality').

Both ぎみ (often written in kanji as 気味) and っぽい describe tendencies or characteristics, but with different nuance. ぎみ suggests a slight or subtle tendency, often related to physical or emotional states, e.g. 疲れ気味 ('a bit tired') or 風邪気味 ('have a bit of a cold'). っぽい implies a more innate trait that gives the appearance or impression of something, e.g. 子どもっぽい ('childish') or 忘れっぽい ('forgetful').

Both っぽい and げ describe perceived qualities, but differ in nuance. っぽい refers to innate behaviors or traits that give a certain impression. For example, 子どもっぽい ('childish') or 怒りっぽい ('quick to anger'). In contrast, げ highlights perceived emotions in others. For example, 寂しげな顔 ('a lonely-looking face').

Both っぽい and そう express appearance or impression, but differ in nuance and usage. そう attaches to word stems and is neutral and often based on observation, e.g. 雨が降りそう ('It looks like it'll rain.'). っぽい is casual and attaches to nouns to mean '~ish' or '~like', e.g. 子供っぽい 'childish'. Unlike そう, it often carries a negative or demeaning tone.

Both ふりをする and っぽい describe imitation or resemblance, but with a key difference in nuance. ふりをする implies pretending to be or do something one is not, as in 知ったふりをする ('pretend to know'). In contrast, っぽい conveys a natural resemblance or tendency, often unconscious or inherent, as in 子供っぽい ('childish').

的 and っぽい are similar in that both can be attached to nouns to turn them into adjectives (or adverbs, in the forms 的に and っぽく). They differ grammatically (的 functions as a な-adjective, while っぽい is an い-adjective), and in nuance. 的 has a wider range of uses, similar to English endings like '-al', '-ly', etc., e.g. 感情 'emotion' vs. 感情的 'emotional'. っぽい is narrower in use, and often carries a derogatory meaning, e.g. 子供っぽい 'childish'.

っぽい and らしい ① both describe being 'like' something, but with different nuances and formality. っぽい, similar to the English '-ish,' refers to having the characteristics of something without being that thing, and is very casual, e.g. 子どもっぽい態度 'childish behavior', e.g. from an adult. In contrast, らしい ① implies embodying a characteristic in a more fitting or expected way, e.g. 子どもらしい笑顔 'a smile just as you'd expect from a child'.

っぽい and らしい② both express resemblance. っぽい is casual, like '-ish' in English, e.g. 子どもっぽい 'childish' (usually with a negative nuance). らしい② implies that someone or something embodies expected traits, e.g. 男らしい 'manly' with a nuance of fulfilling cultural expectations of what a man should be.