Learn English – what’s the difference between “send along” and “send”

The two terms are closely related, and even interchangeable in many cases. However, the two words focus on different things. Alliance is more about mutual interests or benefit, while coalition is more about doing some action.

The use of both terms is not limited to the political context. They can be used in other contexts: military, financial, commercial, technological, and so on. Having said that, I agree that coalition is used most often in the political context for "a temporary alliance of political parties forming a government or of states" (see below).

Here are their definitions, according to Oxford dictionary:

alliance (noun)
1. A union or association formed for mutual benefit, especially between countries or organizations.
1.1 A relationship based on similarity of interests, nature, or qualities.
1.2 A state of being joined or associated.

coalition (noun) A temporary alliance for combined action, especially of political parties forming a government.

Here is a quote from Get Them On Your Side by Samuel B. Bacharach (chapter 5):

Formally defined, a coalition is a politically mobilized collection of interest groups or individuals committed to achieving a common outcome (i.e., resistance or change). Through political mobilization you create a group that has some sense of shared goals and/or a sense of connected interests. A coalition is an alliance for joint action.

In short, a coalition is an alliance for joint action.

I looked up put in the NOAD dictionary, and found this definition:

move to or place in a particular position

Based on that definition, I can understand why you think these two words might be synonymous, but they are not!

The verb put is used in a local context (that is, rarely much further than a room or house), whereas send is used in more of a long-distance context.

For example, for put, we would say:

Put the sofa over in that corner.
Put your dirty plate in the sink.
Put your trash in the garbage can.
Put that laundry basket back downstairs next to the dryer.

whereas for send, we might say:

I am going to send these cookies to Aunt Erma out in Arizona.
Please send me your application via email.
Let's send a ship to the Mediterranean Sea.
We need to send more medical supplies to Uganda.

With mail, mail is almost always sent, unless we are are talking about the individual letters, which can be put anywhere after they have arrived:

I just picked up the mail; where do you want me to put it?
Oh, please put the mail on the desk over there. Thank you.

Of course, English being English, it's not always that straightforward. In the 1960's, was the goal to
put a man on the moon, or to send a man to the moon? According to my guidance, send would be
the better word. So why did John F. Kennedy say in a speech:

I am delighted that this university is playing a part in putting a man on the moon.

I think that's because send sometimes has a connotation of being a one-way trip. We don't expect Aunt Emma will return those cookies, or that Uganda will send back the medical supplies. That's what president Kennedy was emphasizing in another speech, when he said:

...of landing a man on the moon and returning him safely to the Earth.

The verb put can imply putting something down gently or safely, whereas sending a person to the moon says nothing about getting the astronaut back safely.