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be diurnal
diurnal 作表语时表示“白天活动的”，与 nocturnal（夜间活动的）相对。
Many animals are diurnal, while others are nocturnal.
许多动物在白天活动，而其他动物在夜间活动。
白天的；昼间的；日间活动的
先理解核心含义，再看它在真实句子里的用法。
白天的；昼间的；日间活动的
of, belonging to, or active during the day
Many animals are diurnal, while others are nocturnal.
许多动物在白天活动，而其他动物在夜间活动。
医学中也指“昼现的”，如 diurnal filaria（昼现丝虫）。
白天发生的,或主要在白天活动的
Happening or occurring during daylight, or primarily active during that time.
指花朵在白天开放或散发香气,夜间不开放或不散发香气的
Said of a flower that is open, or releasing its perfume during daylight hours, but not at night.
具有24小时昼夜周期的,通常指任务、过程、潮汐或日出日落；昼夜节律的
Having a daily cycle that is completed every 24 hours, usually referring to tasks, processes, tides, or sunrise to sunset; circadian.
Squirrels are diurnal, so you usually see them in the morning and afternoon.
松鼠是昼行性动物，所以你通常在早晨和下午看到它们。
The wildlife park houses its diurnal birds in a sunny enclosure, not a dark aviary.
野生动物园把昼行鸟类放在向阳的围场里，而不是放在黑暗的鸟舍。
After years of working at night, she adopted a diurnal schedule and had more energy.
多年在夜间工作后，她改为白天作息，精力更充沛了。
diurnal 作表语时表示“白天活动的”，与 nocturnal（夜间活动的）相对。
Many animals are diurnal, while others are nocturnal.
许多动物在白天活动，而其他动物在夜间活动。
diurnal 作定语可表示“每天的、昼夜的”，如 diurnal rhythm（昼夜节律）、diurnal variation（昼夜变化）。
The diurnal rhythm of body temperature is a well-known phenomenon.
体温的昼夜节律是一种众所周知的现象。
Not this
He brushes his teeth diurnal.
Use this
He brushes his teeth daily.
diurnal 是形容词，不能作副词；表达“每天”作时间状语应用副词 daily。这里用形容词修饰动词，属于词性错误。
Not this
In summer, the diurnal is longer than the night.
Use this
In summer, the daytime is longer than the night.
diurnal 作名词时指“白昼活动的动物”等专门含义，并不表示“白天/日间”。表示“白天”应用 daytime。这里把形容词误用作名词，属于词性混淆。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
昼夜节律；日节律
The doctor measured the patient's diurnal rhythm.
医生测量了病人的昼夜节律。
昼行动物
Falcons are diurnal animals, hunting during the day.
隼是昼行动物，在白天捕猎。
日变化；昼夜变化
The study recorded diurnal variation in temperature.
这项研究记录了温度的日变化。
昼夜温差；日较差
The desert has a wide diurnal temperature range.
沙漠的昼夜温差很大。
昼夜循环；日循环
The diurnal cycle affects plant growth.
昼夜循环影响植物生长。
周日运动
The diurnal motion of the stars is caused by Earth's rotation.
恒星的周日运动是由地球自转引起的。
Use diurnal naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
diurnal 的 'di' 像 day 的开头，可记作‘每天白天（day）都在’；与 nocturnal（夜间的）对照记。
语域：formal 常见场景：biology、astronomy、medicine 该词属于正式用语，通常出现在学术或专业语境中：生物学里指“日间活动的”，天文学或医学中则指“每日的、昼间的”。日常口语中更常用 daily 或 daytime。
这些词都与 diurnal 的结尾 /ˈɜːnəl/ 押韵：journal /ˈdʒɜːnəl/、nocturnal /nɒkˈtɜːnəl/、eternal /ɪˈtɜːnəl/、internal /ɪnˈtɜːnəl/、external /ɪkˈstɜːnəl/、colonel /ˈkɜːnəl/。注意 diary /ˈdaɪəri/ 和 dial /ˈdaɪəl/ 拼写以 di- 开头，但读音与 diurnal 不同，并非押韵词；不要单凭拼写推断发音。
Dictionary facts from ECDICT, WIKTIONARY.