* فرقی دارند؟ "When" means ?کِی and کِه in Persian. که is equal to "when, where, what, which, that, ..." when those are applied as conjunctions. The words like وقتی که، زمانی که، آنگاه که ، هنگامی که mean 'if', in this case, you can drop که.For example: وقتی [که] تلاش کنی موفق می شوی But when که joins to separated sentences, you can't drop it: وقتی به خانه رسیدم که غذا آماده شده بود

Actually there is no difference between them .It's like we can eliminate "that" from our sentence and it makes no difference. وقتی اومدم خونه! وقتی که اومدم خونه!There are the same and without که is more common in conversations.

They have the same meaning and application and natives use both these in most conditions. But literally, the term "Vaghti ke" is the correct one.

There is no difference between them... in every day persian we usually use "vaghti ke". وقتی که امدم خانه... وقتی امدم خانه Both are correct and have same meaning..

Would you please share that article here, Siavash? :)