Path and trajectory are referred to two different concepts.
Path and trajectory refer to two different concepts.
I want to know the difference of usage are referred and refer here. How does it affect the meaning?
Path and trajectory are referred to two different concepts.
Path and trajectory refer to two different concepts.
I want to know the difference of usage are referred and refer here. How does it affect the meaning?
To complete the answer to the revised question:
Your first sentence could be used as a clause in a context exemplified by "In this theory, path and trajectory are referred to two different concepts: predetermined fate and random chance."
The second statement is simple and can stand alone as a sentence, merely stating that the meanings are different (as I outline below).
trajectory = the curved path that an object follows after it has been thrown or shot into the air
This suggests that trajectory is a special type of path. This definition is consistent with the idea that the geometrically simple path followed by such an object is determined by its initial launch direction and speed, and then by the medium through which it passes.
In contrast, the geometrically complex path followed by something or someone may determined by their own volition and by the circumstances they meet on the way. A path over a mountain is a track that wanders up and down, round obstacles and over them. A trajectory (of a plane or missile) over a mountain is a simple curved track in the air.
The definition of trajectory as a sort of path has led sometimes to careless use (or unnecessary extension of meaning of trajectory) as synonyms for a track through life, for a description of the development of a process such as learning or the progress of a disease.
The two meanings are very different,"refer" is the active voice and "are referred" is the passive voice.
When the active voice is used it means that the subject of the verb carries out the action of the verb, for instance if you say that two people refer to something you mean that they speak of it. There is another use of "refer" which is used when a doctor or other professional sends a patient to see another professional with more specialist knowledge. The professional is said to "refer" the patient or client to a specialist.
On the other hand "are referred" is the passive voice. When the passive voice is used the subject of the verb is acted upon by another agent. If we look at the doctor/patient relationship described above we can say "The doctor referred the patient to the surgeon" (active voice) or "The patient was referred to the surgeon by the doctor" (passive voice). In both cases it is the doctor who has done the referring and the patient who has had the referring done to him but in the passive voice the patient is the subject of the verb "was referred".
What this means for your examples is that when the words "refer" to two different concepts in the active voice it means that they name those concepts in the normal way in the same way as 'car' and 'motorcycle' refer to two different kinds of vehicle. This is the normal use of a noun. The other example says that they "are referred" to two different concepts which means that they are pointed at those concepts by another agency, possibly by a previous sentence. This is a rather unusual use of a noun and I'm not quite sure what it means in this case.