無口 and 沈黙: few words in context and a period of silence
Compare 無口 in work or home settings with 沈黙 after a question or before someone speaks. Keep laughter separate from talkativeness and avoid assigning an unstated motive to silence.
Reading few words with the stated setting
無口 (むくち) concerns reticence or few words. 「無口な職人は作業中ほとんど話さない。」 means “The quiet artisan rarely speaks while working.” Retain both the description of few words and the work setting, rather than turning it into never speaking anywhere.
「兄は家では無口だが、友人の前ではよく笑う。」 means “My older brother is quiet at home but laughs often with friends.” The settings differ, and laughter is explicitly mentioned. Laughing often does not establish that he talks a lot with his friends.
Silence after a question and before speech begins
沈黙 (ちんもく) means silence. 「質問を受けた彼はしばらく沈黙した。」 means “When asked the question, he remained silent for a moment.” The sentence places a period of silence after the question, but does not state the reason for it.
「長い沈黙の後、会長が静かに話し始めた。」 means “After a long silence, the chairperson began to speak quietly.” A long silence is followed by the start of speech. This example prevents a rule that 沈黙 must always be a brief moment.
Few words and silence do not identify a motive
For 無口, read a person's few words together with the setting; for 沈黙, read the period or state of not speaking. This does not make 無口 an unchanging lifelong personality and 沈黙 a necessarily momentary reaction. Someone who says little can also be silent at a particular point.
Silence after a question does not automatically indicate agreement, opposition, deception, or discomfort. Laughter with friends does not give a measure of speech either. Check the setting, amount of speech, period of silence, and any stated next action without adding a hidden cause.
Does the brother being 無口 at home but laughing often with friends establish that he talks a lot with friends?
Show the answer and why
No. The example states few words at home and frequent laughter with friends. Laughter is not the same as a large amount of speech. Likewise, the 沈黙 examples do not let us infer a motive from the period of silence alone.