Like ということ, an expression used for nominalizing a phrase in the fashion of ‘the ~ that ~’, ということだ
makes use of the 助動詞（じょどうし） (auxiliary verb) だ
), and stresses that the nominalized phrase ‘is’ the case. This phrase is often translated as ‘I heard that’, or ‘it is said that’, but literally, it is closer to ‘it is that it’s ~’. The だ
is what gives this expression a high degree of certainty, therefore implying that the speaker has heard the statement elsewhere, and is sure of its validity.
can be added to the end of any phrase that the speaker wants to highlight as being something that is known.
It is said that this well is contaminated.
This fish doesn't smell at all. It means that it’s fresh.
ということだ is regularly paired with other expressions that show the ‘source’ of information, such as によると, or によれば
According to the doctor, (it is said that) this sickness cannot be cured with medicine.
It is said that the criminal is still on the run, according to the Osaka prefectural police.
When ということだ is being used to express hearsay (statements that cannot easily be proven), it can be be rephrased as とのことだ. The literal difference between these two phrases is as follows:
ということだ - It can be explained that (A) is ~ (more emphasis on the information)
とのことだ - The statement of (A) has been applied to ~ (more emphasis on the source that ‘applied’ the information)
It means that the rules differ depending on the area.
It is said that the rules differ depending on the area.
is considered to be more formal than そうだ
when reporting information that has been heard from another source. This is primarily due to ということだ
expressing something that is thought to be a fact, while そうだ
retains the nuance of being something that is a speculation/guess.
I heard that he went on a trip without telling his family.
It is said that he went on a trip without telling his family.