What it means
راستگو (rast-gu) is the Persian word for a truthful person, a truth-teller, someone whose word can be trusted. It is the moral opposite of دروغگو (dorugh-gu, liar) and is built on the same compounding pattern: راست (rast, truth, straight) plus گو (gu, sayer), giving truth-sayer. Calling someone rast-gu is a serious compliment in Persian; it places them in the small category of people whose statements you can build on.
The base word راست carries a fertile spread of senses: true, straight, right (as opposed to left), correct. The truth-telling sense is the one alive in rast-gu, but the underlying image is of straightness, an unbent line between thought and speech.
How to use it
Rast-gu works as noun and adjective, like its opposite. The phrase آدم راستگو (adam-e rast-gu, a truthful person) is the standard reference. Iranian parents teach children راستگو باش (rast-gu bash, be truthful) as one of the first moral instructions.
oun adam-e rast-guyi ast.
He is a truthful person.
او آدم راستگویی است.
be rast-gu hamishe ehteram bezar.
Always respect a truthful person.
به راستگو همیشه احترام بذار.
rast-gu bash ta etemad-et konand.
Be truthful so they trust you.
راستگو باش تا اعتمادت کنند.
The Zoroastrian inheritance
In ancient Zoroastrian thought, truth (اشه, asha in Avestan) stood at the center of the moral cosmos, with the lie (دروغ, drug in Avestan) as its existential opposite. Modern Persian inherits this framework through everyday vocabulary: rast-gu and dorugh-gu are not just descriptive labels for behavior but, in the deep grammar of the language, names for which side of a cosmic divide a person stands on. Iranians may have left the Zoroastrian religion centuries ago, but the moral binary survives in the words.
Where it comes from
Both halves are native Persian. راست (rast) descends from Old Persian rasta, straight, correct, true, the same root that gives English right through shared Indo-European ancestry. گو (gu) is the present stem of گفتن (goftan, to say), an inherited Persian verb. The compound rast-gu is therefore a fully native word, built from two of the oldest Persian elements through the basic compounding pattern. Compare its sibling rast-kar (راستکار, righteous one, doer of right), built on the same first element with the agent noun for doer.
In our voice
If you want to compliment someone seriously in Persian, calling them rast-gu lands harder than calling them honest. The word reaches further back. It says you trust them at the level of who they are.
References
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