A circular area surrounding a breast’s nipple. Your areolas may grow larger, darker, and bumpier when breastfeeding. It’s natural for them to vary in size and color from person to person and at different stages in life.

A remarkable set of instinctive newborn moves. Newborns have a natural instinct to begin feeding shortly after birth. When placed skin-to-skin on your chest, they may move toward your nipple in what’s called the breast crawl.

A bundled pattern of baby feeding. Within the first few weeks of life in particular, but also surrounding growth spurts in later months, your baby may suddenly need to eat much more often than normal, in clusters spanning a few hours at a time. If you’re breastfeeding, this will likely prompt your milk production to increase. While this temporary disruption of feeding patterns might feel alarming, it’s completely normal.

The very first form of breast milk that you start to make, at 16 to 20 weeks of pregnancy. It’s ready to feed your baby shortly after birth and through the first few days of life outside the womb. It’s often called liquid gold, thanks to its rich yellow color, as well as its dense composition of nutrients and antibodies that can boost your newborn’s immune system and jump-start the gut function.

A painful condition whereby breasts become tight and swollen due to an internal buildup of milk, distended veins, and other fluids. Your breasts are most likely to become engorged when you’re first starting to breastfeed.

The practice of feeding a baby breast milk without directly breastfeeding.

Milk removed from breasts with a pump or by hand. You can store your expressed milk in bottles or freezer bags to later feed your baby.

The practice of relying on an infant’s hunger cues—including opening the mouth, fussing, sucking hands, or crying—to determine when to feed a baby, as opposed to establishing or following a regular feeding schedule or pattern. Feeding on demand involves watching out (or listening) for your baby’s hunger cues and quickly responding to them.

A liquid that flows from a breast at the beginning of a regular breastfeeding session. Your foremilk has higher levels of lactose and water, and lower levels of fat, than your other forms of breast milk.

A piece of tissue on the underside of the tongue that connects it to the bottom of the mouth. Your baby’s frenulum plays an important role in feeding and swallowing.

A liquid that flows from a breast at the end of a regular breastfeeding session. Your hindmilk has higher levels of fat, and lower levels of lactose and water, than your other forms of breast milk.

Nipples that either lie flat against the chest or point inward into the body, and that cannot protrude when gently stimulated. While most people who have inverted nipples are born with them, breastfeeding injuries sometimes cause nipples to invert. Inverted nipples can make breastfeeding more challenging.

The process of a baby fastening its mouth around a nipple and areola to begin nursing. A proper latch involves the compression of milk ducts and dynamic movements of the baby’s cheek, chin, tongue, jaw, and neck to create an effective suction. Once latched, your baby’s suckling induces a letdown and further production of your breast milk.

A condition that occurs when the membrane attaching the top gums to the upper lip is so tight, thick, or stiff that it interferes with lip movement and breastfeeding. Lip ties can make lip movement and breastfeeding more challenging.

A condition marked by painful swelling or inflammation of the breasts that can occur when milk builds up in breast tissue or milk ducts become infected. Treatment involves finding the underlying cause and decreasing inflammation. When inflammation progresses, it often leads to an infection that requires antibiotics.

A natural response to a baby’s latch and initial suckling, also referred to as milk ejection reflex (MER). The stimulation of the nerves on your nipple and areola send a signal to the brain to release oxytocin, which prompts the tissue holding the milk inside the breast to release it through the ducts to the skin surface.

The movement of milk from the breast to the baby. The degree or amount of milk transfer is related to milk production; if milk is not being stimulated and removed from your breast, your supply will decrease.

The area of the breast that includes the nipple and surrounding areola. In order for babies to establish a comfortable and effective latch, they need a good amount of the NAC in their mouth. There isn’t a textbook amount that’s just right—many factors, including your baby’s palate and cheek strength, work together to make this possible for all body types, which includes a variety of NAC shapes, colors, and diameters.

A hormone that helps facilitate childbirth, postpartum recovery, lactation, and intimacy. When giving birth, it strengthens your contractions. When recovering from childbirth, it helps control postpartum bleeding. When breastfeeding, it triggers your breasts’ clusters of alveoli sacs, called lobules, to release the milk stored in them while widening your milk ducts for easier flow to the nipple and contracting your uterus. And during moments of physical intimacy, it induces pleasure, as it travels from the brain into the bloodstream, giving it an affectionate nickname: the love hormone.

An inflammatory obstruction in either the ductal system or nipple that hinders milk flow through the breast. This may feel like a tender or firm lump, a warm and painful localized spot, or a wedge-shaped area of swelling anywhere on the breast.

A hormone that contributes to more than 300 processes in the body, most notably breast tissue development and lactation in women. Your prolactin levels are typically high when you’re breastfeeding or pregnant, and they spike when your baby stimulates your nipple through suckling. It drives the actual milk production from the glandular tissue in the breasts.

A baby’s natural instinct to move its head back and forth in search of a nipple. Your baby was born with this survival reflex.

A common fungal infection in babies’ mouths resulting from an overgrowth of a yeast called Candida albicans. Oral thrush can be passed from mother to baby when breastfeeding, and it can be identified by a cottage cheese-like white growth on the tongue, gums, and inner cheeks that does not wipe off with a finger or washcloth.

An out-of-sync interplay between a baby’s tongue frenulum, mouth shape, palate height, cheek width, and other anatomical factors. Because it restricts a baby’s tongue movement, it can present challenges to breastfeeding, infant growth, and milk production.