Q:

What is the difference between "arc", "hen" and "season" when categorizing anime series sub-stories?

I always see that different stories in the same anime series are usually called with either "hen", "arc" or "season" as seen in the examples below.

Hen (編)
JoJo no Kimyou na Bouken - Stardust Crusaders - Egypt Hen
Alps no Shoujo Heidi: Alm no Yama Hen
Hokuto no Ken: Raoh Gaiden Gekitou-hen / Hokuto no Ken: Raoh Gaiden Junai-hen
Arata naru Sekai: Kako-hen / Arata naru Sekai: Gendai-hen / Arata naru Sekai: Mirai-hen
Arc
One Piece: Arlong Park Arc / One Piece: Sabaody Island Arc
Bleach: Arrancar, The Arrival Arc / Bleach: Arrancar, The Hueco Mundo Sneak Entry Arc
Naruto: Chuunin Exam Arc / Naruto: Pain's Assault Arc
Season
Aldnoah.Zero 2nd Season
Girls Bravo: First Season
Moonlight Mile 1st Season: Lift Off

I observed these differences:
Hen: Always added at the end of the title. Sometimes it is made suffix with a hyphen.
Arc: Used to logically divide long running series.
Season: Always used with a number starting from 1.
Why do they choose one over another? For example, why don't we say "Moonlight Mile: Lift Off Hen" or "Naruto: Chuunin Exam Season"? Is this only a matter of choice or do they differ in meaning?

A:

Arc is English word and Hen is Japanese. They both indicate storylines (separation by what is happening in story), whereas season is used to split the anime by industry and commercial timeline (commonly by actual seasons: Winter 2015, Fall 2015). Multiple arcs may comprise a single season or multiple seasons maybe needed to finish a single arc.
Take One Piece for example. Season 3 and Season 4 of One Piece anime actually share arcs.  

