1. If you are stressed, you feel tense and anxious because of difficulties in your life.
2. If someone is stressed out, they are very tense and anxious because of difficulties in their lives.
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The above are form Collins Dictionary.
Q1: Does it mean that there is a difference between 'stressed' and 'stressed out'? In other dictionaries, I could find that 'stressed out' is the informal form for 'stressed.' Does it mean 'stressed out' is 'stressed?
Q2: In sentence 2, why does 'they' refer to 'someone'?
Q1 - There is no difference between "stressed" and "stressed out." The latter simply has an extra word.
Q2 - "they" and "their" (plurals) are incorrect since "someone" is singular.
Q1: Yes, there is a difference between "stressed" and "stressed out," although they are closely related. Generally, "stressed out" is an informal expression that intensifies the feeling of being stressed. It suggests a higher level of tension and anxiety compared to simply being "stressed." However, both terms essentially convey the same meaning of feeling tense and anxious due to difficulties in one's life.
To understand the difference, it's helpful to know that language can have informal or colloquial expressions that are not always captured in formal dictionaries. In this case, the Collins Dictionary acknowledges "stressed out" as an informal variation of "stressed." So, you can consider "stressed out" as a more vivid and intense way of expressing stress.
Q2: In sentence 2, the pronoun "they" is used as a gender-neutral pronoun referring to an unspecified person or people in general. It is a common practice in English to use "they" to refer to a singular person when their gender is not specified or when they identify as non-binary. This usage allows for inclusivity and avoids using gender-specific pronouns like "he" or "she." So, in this context, "they" refers to a person who is feeling very tense and anxious due to difficulties in their life.