Distiction.

السلام عليكم

Affect or Effect

Question:

Does the weather affect or effect your mood?

Answer:

affect

How to Remember It:

The simplest distinction is that affect is almost always a verb, and effect is usually a noun.

It may help to remember that the verb – the "action word" – starts with "a": affect is an action.

Desert/Dessert

Question:

If you receive an appropriate punishment, did you get your just deserts or just desserts?

Answer:

just deserts

How to Remember It:

This word is unrelated to deserts of the sand and cactus kind, and it isn't about the desserts that provide a sweet finish to a meal.

Instead, this deserts comes from the same word that gave usdeserve. (Oddly, it's pronounced like desserts.)

Stationary/Stationery

Question:

Do you buy your writing paper in a store that sells stationary or stationery?

Answer:

stationery

How to Remember It:

For one, consider the histories of these words.

Stationery comes fromstationer, a word that in the 14th century referred to someone who sold books and papers. What the stationer sold eventually came to be referred to by the noun stationery ("materials for writing or typing" and "letter paper usually accompanied with matching envelopes").

Meanwhile, the adjective stationary has always been used to describe what is fixed, immobile, or static.

Here's another way to remember it: stationery is spelled with an "e," like the envelopes that often come with it.

Principal/Principle

Question:

Is the person in charge of a school the principal or theprinciple?

Answer:

principal

How to remember it:

A couple of mnemonics based on letters are useful here: the principal is your pal. Principle, like rule, ends in "l-e."

Source: http://www.merriam-webster.com

Wassalam :)