That is only the lexical form. If you want the actual meaning then you must go further than just the meaning of the pres. act. ind. lexical form.
The form of the verb will determine a lot of its meaning. Many words are only used in a particular form. One would never say I gone to the store. I go to the store has a very different meaning than I went to the store.
If you want to get the basic meaning that is different. If you want to get the actual meaning then you must look at the actual word not just the lexical form.
I don't usually bother to with the rest of the conjugation, including the other voices, moods, tenses, etc. Thus the infinitive, or the Present Active Indicative of Chairo is used 74 times just as luo in all of its various forms is used 43 times.
The infinitive form of chairo is used only seven times. Six of those as a greeting and one as a command to rejoice.
Does it really make a difference if the word is translated He loosed or They are loosing? No. The word is the same "to loose."
It makes a huge difference.
I am killing is much different than I killed.
What you described is the action. It could be the difference between a punctiliar action and a continual action.
For example in 1 Peter 1:4 the word translated
reserved in heaven is a perfect passive participle feminine singular accusative. That particular participle puts the emphasis on the existing result. The act descibed will be antecedent to the time of the leading verb, but the state that has resulted from that past action wil be contemporaneous with the leading verb.
The action described in 1 Peter 1:4 is much different than
reserved just being a past tense verb. My salvation being reserved is not just a past tense verb. It is a past tense decision (action) and continues on into the future.
Participles are used very differently than verbs. That is much like asking what is the difference between an adjective and a noun.
It comes from the same word. Your objection therefore is quite invalid. If you know nothing about the conjugation of a Greek word then I suggest you learn. The ending of the word which simply gives the way it is used really makes no difference. Chairo means either farewell or Greeting. But those are minor distinctions as to its greater meaning of rejoice.
Remeber you originally talked about chairos which does not exist anywhere. Chairo does.
You refer to an English Concordance. I used a Greek concordance of the NT, for the NT was written in Greek. The OT was written in Hebrew. "Presbuteros" won't even be found in the OT, obviously. It is a NT word only.
It is found in the LXX.
It is used 66 times in the NT, and is translated 3 different ways. The biggest difference is that it is a noun and not a verb.
Now take a look at the word episkopos and notice the time when it was used.