In Japanese some parts of words or letters often get left out in order to
shorten them, but what is this phenomenon called? Does anyone know? Do you
know the English terminology? The Japanese terminology?

Two examples ...

けれども becomes けど

かもしらない becomes かも
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2018-05-24T03:08:14.287
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2018-06-23T10:56:09.917
2018-05-24T05:32:50.573
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linguistics
Terminology for leaving out parts of words
けど or けれど are defined by コトバンク as 砕{くだ}けた言い方 (plain speech; colloquialisms).

かも is defined as a 略｛りゃく｝ (abbreviation) of かも知れない by the same source.

In general, however, I believe that 略 would be commonly understood in most
cases.
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2018-05-24T04:00:12.497
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2018-05-24T05:27:27.460
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There are two terms related to what you are talking about:

> 縮約｛しゅくやく｝ - contraction

for example: けれども → けど、なければ → なきゃ、俺のうち → 俺んち、しておいて → しとって｡｡｡

> 略語｛りゃくご｝ - abbreviation

for example: 高等学校 → 高校、国民健康保険 → 国保｡｡｡

The definitions do not seem to be very strict however, and I have seen people
and dictionaries refer to everything as 略(語）, whereas scientific literature
seems to prefer to distinguish 略語 from 縮約形、縮約語、短縮形 among others...

For abbreviated names, the term 略称｛りゃくしょう｝ is used instead.
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2018-05-24T10:09:30.117
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