(n)sign, marka perceptible indication of something not immediately apparent (as a visible clue that something has happened)“he showed signs of strain”, “they welcomed the signs of spring”
(n)polarity, signhaving an indicated pole (as the distinction between positive and negative electric charges)“he got the polarity of the battery reversed”, “charges of opposite sign”
(n)augury, sign, foretoken, preindicationan event that is experienced as indicating important things to come“he hoped it was an augury”, “it was a sign from God”
(n)signa fundamental linguistic unit linking a signifier to that which is signified“The bond between the signifier and the signified is arbitrary” (de Saussure)
(v)sign, signal, signalize, signalisecommunicate silently and non-verbally by signals or signs“He signed his disapproval with a dismissive hand gesture”, “The diner signaled the waiters to bring the menu”