allo-, alter- +
(Greek: allos, other; Latin: alter, other)
The term "other" can be either positive and/or negative
Some of the words that come from the root meaning "other" seem to have negative elements. One exception is the word altruism which means "unselfishness".
An alien, someone who comes from another country, is often regarded with suspicion because he or she is a stranger.
Allergy, having a negative response to other things; such as, certain foods, animals, pollen, etc.; is another example.
2. An assumed name.
"To keep the police off his tracks, the man assumed an alias every time he moved."
2. Strange in a situation; not natural.
"To the alien who was trying to learn English, it was alien to protrude his tongue in order to pronounce th."
"George Orwell's Animal Farm novel is an allegory in which animals behave and talk like humans."
2. Sensitiveness to certain foods, animals, pollen, etc.
"After being in the room with the cat for five minutes, her allergy began to act up and she started to sneeze."
"When she lost weight, she had to have all of her clothes altered to fit her new size."
2. A very close friend.
"Dr. Jekyll and Mr. Hyde were alter egos in a tale of horror."
2. To take turns.
"James alternated with Sam in taking the night shift on alternate weeks."
2. Another choice.
"Betty's parents could not longer pay for her college fees, and so she had no alternative but to find a part-time job."
2. Acting in an unselfish way to help others.
"When the earthquake struck, people from all over the world, out of a sense of altruism, volunteered their help for the victims."