noun, used as a prefix, noun which may take the genitive case particle 'no', noun
Used as a prefix or with の to mean something is done directly, without an intermediary. Often appears in compounds like 直談判 (direct negotiation) or 直に (じかに, directly).
See also: 直に (じかに)
社長と直に話す機会はめったにない。
I rarely get a chance to speak directly with the company president.
直の取引でコストを下げた。
We reduced costs through direct transactions.
直接 is the standard word for 'directly' in most contexts. 直 (じか) is more limited, often used as a prefix or in set phrases, and carries a nuance of 'without going through someone/something else'.
The reading じか is a native Japanese reading (kun'yomi) of the kanji 直, which broadly means 'straight' or 'direct'. The prefix/noun usage is an extension of this core meaning.