Latch
Also called latch on, latching, latched, deep latch, shallow latch, relatch
The latch is how a baby takes hold of the breast to feed, with the nipple and part of the darker skin around it in the mouth. It's a verb too: a baby latches, or latches on, and parents talk about a deep latch or a shallow one.
How it's said
But we are struggling with the latch.
I think it's the latch breaking as he's not latched deeply enough.
Her initial latch was fine; the midwives would check she was on OK and then go...
Who says it
In the UK the NHS also calls it attachment, as in its guide to positioning and attachment.
Where it came from
Latch goes back to Old English læċċan, to grasp or take hold of, the same root as the latch on a door. Dictionaries now list the baby sense on its own: of a breastfeeding baby, to connect to the breast, or in Cambridge's words, to attach its mouth to its mother's breast to drink milk.
The word works as a noun and a verb, and it grew a family of forms: latch on, relatch and unlatch. A good latch is described as one where the nipple and a large part of the areola are in the baby's mouth, and parents trade tips for turning a shallow latch into a deeper one.