1. Indo-European languages

-are a family of several hundred related languages and dialects. There are about 445 living Indo-European languages, according to the estimate by Ethnologue, with over two-thirds (313) of them belonging to the Indo-Iranian branch alone.

2.prefix, suffix, roots

A prefix is an affix which is placed before the stem of a word. Adding it to the beginning of one word changes it into another word. Particularly in the study of languages, a prefix is also called a preformative, because it alters the form of the words to which it is affixed. The word prefix is itself made up of the stem fix (meaning "attach", in this case), and the prefix pre- (meaning "before"), both of which are derived from Latin roots.

A suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns or adjectives, and verb endings, which form the conjugation of verbs. Particularly in the study of Semitic languages, a suffix is called an afformative, as they can alter the form of the words.

A root, or a root word, is a word that does not have a prefix or a suffix . The root word is the primary lexical unit of a word, and of a word family (root is then called base word), which carries the most significant aspects of semantic content and cannot be reduced into smaller constituents. Content words in nearly all languages contain, and may consist only of root morphemes. However, sometimes the term "root" is also used to describe the word minus its inflectional endings, but with its lexical endings in place.

3.aptitude, altitude, attitude

aptitude -is a component of a competency to do a certain kind of work at a certain level, which can also be considered "talent". Aptitudes may be physical or mental. Aptitude is developed knowledge, understanding, learned or acquired abilities (skills) or attitude. 

altitude-The absolute height of a location, usually measured from sea level or a vertical distance.

attitude-The position of the body or way of carrying oneself; posture or disposition or state of mind.

4.

de-down; away from

depreciate- To lessen in price or estimated value; to lower the worth of; to represent as of little value or claim to esteem; to undervalue. 

decline- To move downwards, to fall, to drop. To become weaker or worse. To bend downward; to bring down; to depress; to cause to bend, or fall. 

5.

dia-go through

dialog- A conversation or other form of discourse between two or more individuals or in a dramatic or literary presentation, the verbal parts of the script or text; the verbalizations of the actors or characters. 

dia-the line go through any squares

diameter- Any straight line between two points on the circumference of a circle that passes through the center of the circle.

6.video

https://www.youtube.com/watch?v=xXrgD8_VtMA 十分鐘讀懂英文