"He is strange."
Translation:Er ist komisch.
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""seltsam" implies to something rather foreign, something that is strange to you, something "weird" or "strange", like an unexpected behaviour, like if Obama would skate into the conference room to greet the ministers of each nation you would think "Das ist ein seltsames Verhalten von Obama." because he isn't supposed to do that in his position.
"komisch" is meant in a rather comedic way of "funny" or the "funny" as in saying something is rather strange. "That's funny, I thought he said he was a lawyer".
In english you also say "that's weird" or "that's funny" if you are puzzled about something you don't know or find strange, right? So, there you go."
In English, we use he/him and she/her when talking about humans, (and in some cases where the natural (biological) gender is known, i.e an animal), and it when the gender's unknown or when referring to (inanimate) objects. This is mainly because English has mostly dropped grammatical gender, with some few exception (that in my opinion don't count as exceptions because they still refer to natural gender: rooster (m), hen (f), chicken (n))
On the other hand, in German, we use "er/ihn/ihm", "sie/sie/ihr" and "es/es/ihm" in respect to grammatical gender, and not natural (biological) gender.
That said, when translating a sentence; context provided, a word that is grammatically masculine in German, if it's an inanimate object, a correct translation of "er" would be "it" in English
Here's an example:
Der Himmel ist lila. Er ist seltsam.
The sky is purple. It is mysterious.