An eyelash is one of the hairs that grows at the edges of the top and bottom eyelids, spanning outwards and away from the eyes. The lashes grow in up to six layers on each of the upper and lower eyelids. Eyelashes serve to protect the eye from debris, dust, and small particles, and are highly sensitive to touch, thus providing a warning that an object is near the eye, which then reflexively closes or flutters to rid the area of the object. The eyelid margin from which lashes grow is among the most sensitive parts of the human body, with many nerve endings enveloping the roots of the lashes, giving it sensitivity to very light tactile input even at the tips of the lashes, enabling it to trigger the blink reflex when touched. Eyelashes are also an important component of physical attractiveness, with long prominent lashes giving the illusion of large, gazing eyes, and drawing attention to the eyes.

बरौनी, नेत्र पलक के छोर पर उगे बाल को कहते हैं। बरौनियां बाहरी पदार्थों जैसे कि धूल-मिट्टी को आंखों में जाने से रोक कर आंखों की रक्षा करती हैं साथ ही यह स्पर्श के प्रति बेहद संवेदनशील होती है और किसी भी बाहरी वस्तु जैसे कि कोई कीट या तिनका आदि के प्रति व्यक्ति को सचेत करती हैं ताकि वो अपनी आंखें तुरंत बन्द कर सके। अक्सर हिन्दी में अज्ञानसवरूप बरौनी के लिए पलक शब्द का प्रयोग होता है जो सही नहीं है।