Baby feeding glossary

The five that matter most

If you read nothing else here: flange decides whether pumping is comfortable and productive. Nipple flow causes more bottle problems than the bottle does. Closed system is what makes a pump easy to clean and safe to buy used. Venting is the real difference between anti-colic bottles. Paced bottle feeding is a free technique that helps more than most purchases.

A to Z

Anti-colic

An unregulated marketing term for a bottle with a venting system designed to reduce how much air a baby swallows. It describes engineering, not a treatment for colic.

Areola

The darker area of skin around the nipple. It matters here for one reason: when you measure for a flange size you measure the nipple only, not the areola. Including it is the most common measuring error.

Borosilicate

A type of glass that copes with sudden temperature change far better than ordinary soda-lime glass. It is what good glass baby bottles are made from, and it is what makes freezing milk in glass reasonable.

Closed system

A breast pump with a barrier that stops milk ever reaching the tubing or the motor. Easier to clean, and the only kind of pump worth using second-hand with a new set of parts.

Colostrum

The thick, concentrated first milk produced in the days after birth, in very small quantities. Because there is so little of it and it is sticky, hand expression or a manual pump collects it far better than a machine does.

Combination feeding

Feeding a baby with both breast and bottle, whether the bottle contains expressed milk, formula, or both. Also called combo feeding or mixed feeding. It is a completely normal way to feed a baby.

Cycle speed

How fast a breast pump alternates between suction and release, measured in cycles per minute. Fast and shallow cycles are used to trigger let-down; slower, deeper cycles move more milk once it is flowing. Being able to adjust it separately from suction strength is one of the most useful features a pump can have.

Elastic nipples

Nipple tissue that stretches unusually far into the flange tunnel under suction. It can make standard flange sizing uncomfortable and unproductive, and it usually needs a smaller flange and lower suction. Worth raising with a lactation consultant rather than solving by buying more flanges.

Engorgement

Breasts that are overfull, hard and often painful. A manual pump or hand expression is frequently the more practical tool for relieving it than an electric pump. Persistent or painful engorgement, or any redness and fever, is a reason to contact a clinician.

Exclusive pumping

Feeding a baby breast milk entirely by bottle, with all of it expressed by pump. Usually six to eight sessions in 24 hours, which changes which pump features matter: output, comfort and how many parts you have to wash.

Flange

The funnel-shaped part of a breast pump that sits against the breast. Getting the size right affects comfort and output more than the brand of pump does, and most pumps ship with only one or two sizes.

Hospital grade

A marketing phrase more than a standard. In practice it describes a pump with a motor rated for multiple users, usually rented rather than bought. It does not automatically mean more milk for you.

Let-down

The reflex that releases milk from the breast. Most decent pumps have a massage or stimulation mode designed to trigger it, and warming functions exist because warmth can help it happen more easily.

Nipple flow

How fast milk comes out of a bottle nipple under a baby's suck. Levels are numbered differently by every brand, so a level 2 in one range is not a level 2 in another. A mismatched flow rate causes more feeding problems than the wrong bottle does.

Paced bottle feeding

Feeding with the baby upright and the bottle close to horizontal, with deliberate pauses, so the baby controls the pace rather than gravity. It reduces gulping and swallowed air and makes moving between breast and bottle easier.

Power pumping

Clustering short on-off pumping sessions within about an hour to mimic a baby's cluster feeding, usually attempted to increase supply. Whether it is right for you is a lactation consultant question, not a gear question.

PPSU

Polyphenylsulfone, a high-performance plastic used in premium baby bottles. It tolerates repeated sterilizing without clouding or degrading, and it is much lighter than glass. Its natural amber tint often looks like staining even when the bottle is clean.

Sanitize

Reducing germs on an item that is already clean, by boiling, steaming or a weakened bleach solution. Per CDC guidance it is recommended daily if a baby is under two months old, was born premature, or has a weakened immune system. It is a step after cleaning, never instead of it.

Soda-lime glass

Ordinary glass. It is more likely to crack under sudden temperature change than borosilicate, which is why it is the less suitable choice for a bottle that goes from freezer to warm water.

Suction strength

How hard a pump pulls, usually measured in millimeters of mercury. Almost every modern pump has more suction than you should be using, and the highest setting is rarely the most productive. Comfort gets more milk than strength does.

Venting

A bottle's mechanism for letting air in to replace the milk going out, so a baby is not sucking against a vacuum and swallowing air. Designs range from a simple valve in the nipple to an internal tube, and the more effective ones add parts to wash.

Wearable pump

A breast pump with no tubes and no separate motor: the whole machine, battery included, sits inside a bra. It trades a little output and more parts to wash for the ability to pump while doing something else.

Terms we deliberately do not use

A short note on language, because some of the vocabulary in this category is doing work other than describing things.

• "Breast is best." Breast, bottle, formula, combination — all of them feed a baby. We are not going to imply there is a correct way to do it.
• "Medically reviewed" and "our experts". There is one author on this site, Ryder M., and no clinical review board. Saying otherwise would be a fabrication. See about.
• "Game-changer" and "must-have". A bottle warmer is not a must-have. We would rather tell you when to skip something.
• "Hospital grade" as a selling point. Defined above, and rarely what a consumer buyer needs.

Where these definitions come from

Anything touching hygiene, storage or safety is checked against primary sources rather than paraphrased from other review sites: the CDC on cleaning and sanitizing infant feeding items, the CDC on milk storage and pump hygiene, the AAP on starting solids, and the FDA on BPA in food contact materials.

Where a term is clinical rather than technical — supply, reflux, tongue tie, allergy — we define it only as far as understanding a product requires, and point to a clinician for the rest. That boundary is set out on our editorial policy page.