aliasは「別名」を意味し、語源はalius（別の）に由来します。同義語はpseudonym, false name, bynameです。
Alias means “a false name”, and the etymology comes from alius (another). The synonyms are pseudonym, false name, byname. Let’s see an example sentence.
Spy uses an alias for checking in the hotel. The con artist lives under an alias.
Alias is also used as a computer term. Alias is a MacOS soft link, equivalent to a Windows shortcut.
Alibi means “proof of being not culprit”, and the etymology comes from alius (different). The original meaning is Latin alibi (somewhere else).
An alibi is a proof that a certain person was not in the scene when the incident occurred. Alibi is an important clue to identify the criminal. A suspect who can prove alibis is unlikely to be a culprit. However, in detective stories, the culprit makes a fake alibi with tricks. Detective broke fake alibi by reasoning, witness testimony and evidence.
Alien means “different from what you get used to”, and the etymology comes from alienus (belonging to others). The synonyms are strange and odd.
Alien means that the environment is quite different from the previous one and can not be accepted. Let’s see an example sentence.
The lives of the poor are alien to rich people. People just after changing jobs feel confused about the alien working environment. Internet is alien to the elderly people. Children adapt quickly to alien surroundings.
The second meaning of alien is “foreigners” and synonyms are foreign.
It is mainly used as a term of law and administration. Since alien has strong administrative nuances, in daily conversation, we express it as “people from other countries”. Let’s see example sentences.
Alien residents are staying from the country with an entry permit. Illegal aliens are illegally staying in that country. The alien registration card was abolished in Japan in 2012, and now residence cards are spreading instead.
Alienate means “to isolate”, and the etymology comes from alius (different). The synonym is isolate.
Alienate means that certain people become uncomfortable within the group. Let’s see an example sentence.
Those who do domineering behavior alienates their friends. An idol scandal alienates her fans. Insensitive person will be alienated from the group. Not communicative person is alienated from his company. Neet and shut-in are alienated from society.
Alter means “to change”, and the etymology comes from alter (different). The synonym is change.
Do not confuse it with “altar” of homophone. Let’s see an example sentence.
The Internet dramatically altered our lives. Whatever the politician defines, nothing can alter the fact that Japan’s declining birthrate and elderly population is progressing. Even if you make a mistake in delivery by online shopping, you can alter it immediately. Ten years have passed and the old cityscape totally altered.
alternateは「交互の」を意味し、語源はalter（片方）に由来します。日常会話ではevery other (day, week, Monday)の方が使われます
Alternate means “turn by turn”, and the etymology comes from alter (one side).
However, every other (day, week, Monday) is used in everyday conversation. Let’s see an example sentence.
People with low physical strength work on alternate days. People with ambition go to the English conversation circle on alternate weeks. Some municipalities collect coarse garbage on alternate Mondays. Alternate is used in the fields of math and computer.
Junior high school students learn corresponding angles and alternate angles in mathematics class. Alt on the keyboard stands for alternate key.
Alternative means “can be used instead”, and the etymology comes from alter (one side). The original meaning is Latin alternare (done in turn). Synonyms are substitute, alternate. Let’s see an example sentence.
When planning a picnic or athletic meet, you should also set an alternative date in case of rain. When the road is closed, the car navigation system instructs us an alternative route. If you deny the opponent’s plan, you should prepare an alternative plan.
The second meaning of alternative is “different from conventional”. The opposite term is conventional. Let’s see an example sentence.
Developed countries are looking for alternative energy to replace fossil fuels. With the spread of the Internet, alternative ways of life like bloggers, affiliate earner and YouTuber became possible. Massage, acupuncture and moxibustion, aromatherapy etc are classified as alternative medicine.
Altruism means “helping for others”, and the etymology comes from alter (different) and ism (way of thinking). The opposite term is egoism.
Altruism means a way of thinking to help other people regardless of their own interests. Let’s see an example sentence.
We practice altruism by helping others in trouble before us. Reciprocal (or mutual) altruism is to help others without expecting immediate return, expecting long-term return. Simply put, it is to help people who are in trouble and scratch their back.
Reciprocal altruism is used in behavioral economics and game theory. A representative example of reciprocal altruism is the blood exchange of vampire bat. A generous bat can be helped in a pinch, but a stingy bat will be kicked out of herd.