How do I enter adult, child and infant names in Amadeus?

When

You add passengers to a PNR — including children, a baby on a parent's lap, or a baby with its own seat.

Names exactly as in the passport (surname / first name, no nicknames). Children's and infants' dates of birth.

#	Entry	What it does	Why
1	`NM1SMITH/JOHN MR`	One adult.	Surname / first name then title.
2	`NM3LEE/SAM MR/JOAN MRS/TOM MR`	Three passengers, same surname.	The number = how many names follow.
3	`NM2SCHWARZ/MANFRED MR/SABINE MISS1BLACK/ANDREW MR`	Two surname groups in one entry.	Several families at once.
4	`NM1SIMPSON/MAGGIE(CHD/01JAN20)`	A child with date of birth.	Child fares need the type and age.
5	`NM1LEAVEY/KIM(INF/MICHAEL/18MAY25)`	An adult travelling with an infant (same surname).	A lap infant is attached to the adult, not a separate name.
6	`NM1BROWN/SIOBHAN(INFTROY/HANNAH/10SEP24)`	Infant with a different surname.	Surname written straight after `INF`.
7	`NM1WATSON/JANE(INS)`	An infant with its own seat.	An infant in a seat is priced and seated like a passenger.
8	`NM1JONES/TOM(YTH)`	A passenger type code (youth).	Special fares need the type.

RTN lists the names; the infant shows under its adult; children show (CHD/…).

The number after NM counts the names of that entry, not the infant (step 5 is NM1).
A lap infant takes no seat: sell seats for adults and children only.
Pricing a child or infant needs the name element with the type; without names Amadeus prices adults (see Pricing by passenger, passenger type and discount (children, infants, youth)).
Name errors are expensive after ticketing — many airlines do not allow a name change on an issued ticket. Check spelling before TTP (see Correcting a name, and when the airline allows it).
Extra seat for comfort or for a cello: NM2ADAMS/ARTHUR MR(IDEXST)/EXST or …(IDCBBG)/CBBG — the airline decides whether one or two tickets are needed.