gateway drug

Noun

 * 1) An addictive substance that is seen as relatively harmless by itself, but is believed to encourage the user to experiment with more harmful substances.
 * 2)  Any thing or area of interest that tends to lead to deeper involvement.

Translations

 * Chinese:
 * Mandarin:
 * Danish:
 * Finnish:
 * German:
 * Hungarian: kapudrog
 * Portuguese: droga de entrada
 * Russian:, ста́ртовый нарко́тик, перехо́дный нарко́тик, ключево́й нарко́тик