What is difference between 熱を出す and 熱が出る


I know that [**熱が出る (netsu ga deru)** means to have a
fever](https://ejje.weblio.jp/sentence/content/%E7%86%B1%E3%81%8C%E5%87%BA%E3%82%8B).

Example:

> 風邪を引いたら、39℃の熱が出た。
>
> Kaze wo hiitara, 39C no netsu ga deta
>
> When I caught a cold, I had a fever of 39C.

**What does 熱を出す (netsu wo dasu) mean?**

These are the examples I have:

>   1. でも熱出して寂しいって言ってた。
>

>
> Demo netsu dashite sabishii tte itte ta
>
>   2. 彼女は体が弱いので、何かあるとすぐに熱を出す。
>

>
> Kanojo wa karada ga yowai no de, nanika aru to sugu ni netsu wo dasu




The difference relates to the more general difference between transitive and
intransitive verbs, with transitive verbs being accompanied by an active agent
which is a causal factor.

In your examples, the intransitive verb 出る is used to state a fact that the
heat/fever is happening of its own accord, i.e. 熱が出た = I have a fever. By
using the transitive verb 出す, there is more emphasis on the active agent. This
is sometimes used when referring to things like chemical reactions, where the
reaction 'gives off heat', i.e. there is something which is actively causing
the release of heat. For example,
[高い熱を出す性質](https://ejje.weblio.jp/sentence/content/%E7%86%B1%E3%82%92%E5%87%BA%E3%81%99)
(the property of giving off heat). In your example, 体が弱いのですぐに熱を出す is
emphasizing the causal factor of her weak constitution as being responsible
for the fever. It's a subtle nuance, but with 熱が出る it's simply stating a fact
and with 熱を出す it's pointing to the active agent which is causing the fever.




The difference relates to the more general difference between transitive and
intransitive verbs, with transitive verbs being accompanied by an active agent
which is a causal factor.

In your examples, the intransitive verb 出る is used to state a fact that the
heat/fever is happening of its own accord, i.e. 熱が出た = I have a fever. By
using the transitive verb 出す, there is more emphasis on the active agent. This
is sometimes used when referring to things like chemical reactions, where the
reaction 'gives off heat', i.e. there is something which is actively causing
the release of heat. For example,
[高い熱を出す性質](https://ejje.weblio.jp/sentence/content/%E7%86%B1%E3%82%92%E5%87%BA%E3%81%99)
(the property of giving off heat). In your example, 体が弱いのですぐに熱を出す is
emphasizing the causal factor of her weak constitution as being responsible
for the fever. It's a subtle nuance, but with 熱が出る it's simply stating a fact
and with 熱を出す it's pointing to the active agent which is causing the fever.

