Then  - (WW) The Greek word translated as "then" is usually translated as "but." It joins phrases in an adversarial way. Since it always falls in the second position, translating it as "however" often captures its feeling better.

the -- The word translated as "the" is the Greek definite article. The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

lord  - The word translated as "lord" means "lord" and "master." The standard English word for one who controls slaves is the master. It is, however, the word translated as "lord" to refer to God.

of -- This word "of"  comes from the genitive case of the following word that requires the addition of a preposition in English.  The most common is the "of" of possession.

that  - The word translated as "that" is an adjective that highlights its noun as being in a specific place or time from a word that means "there." Here, it refers to the slave laying on the floor.

missing "the"  -- (MW) The untranslated word is the Greek definite article, "the." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those"). See this article for more. 

servant  - The word translated as "servant" is the word for slave, but it also means a person held in bond for a debt, which is clearly its meaning here. However, using "bondsman" loses the "master" and "slave" contrast.

was -- This helping verb "was" indicates that the verb is passive. Helping or auxiliary verbs are needed to translate the Greek verb forms into English. Technically, it could be the middle voice as well, where the subject acts on themselves, but we would use passive in either case.

moved with compassion,  - (WF, WP) "Moved with compassion" is from a verb that means to "to feel compassion." It is not an active verb but a verb in the form of a verbal adjective, particle, "feeling compassion." It is a New Testament word. It is from a word that means "bowels." Bowels were considered the seat of compassion. So its sense is feeling something in your guts, so "movement" is appropriate. Since the form is a passive, participle, "being moved."

and -- (IW) There is nothing that can be translated as "and" in the Greek source. It was added because the previous verb was translated as active rather than a participle.

loosed  - (CW) "Loosed" is from a verb that means "to loose from," "to set free," and "to discharge." Interestingly, in another context the word means "to destroy utterly," "to lose," and "to perish." It is not the common word used to mean "loose," which is its Greek root, but a more complicated word meaning "loosed from." Our word "release" works well.

him,  - -- The word translated as "him" is the Greek word commonly translated as third-person pronouns in English.  

and  - The Greek word translated as "and" is used as the conjunction "and," but it also is used to add emphasis ("also")

forgave  - -- The word translated as "forgave" primarily means "to let go" or "to send away." This same word is usually translated as "leave," "forgive," "suffer," and "let" in the New Testament. This is Jesus's first word in the Gospels (Matthew 3:15) when he tells John to "suffer" baptizing him. It is often translated as "to leave" or "to let" in the Gospels. It is first translated as "forgive" in the Lord's Prayer (Matthew 6:12) where it is applied to forgiving debts. It has the sense of leaving something alone and letting it drop.

him -- The word translated as "him" is the Greek word commonly translated as third-person pronouns in English.  This verb could be an indirect object, as translated, but it could also be a pronoun referring to the debt, at the verb.

the -- The word translated as "the" is the Greek definite article. The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more. 

debt - (CW) "Debt" is a noun that means "loan." Jesus only uses this particular word once, though he does use another unrelated word for "debt" that he also uses only once in the Lord's prayer, Matthew 6:12. Jesus uses the other, more common word, throughout the rest of this parable.