FA (http://www.lojban.org/en/publications/reference_grammar/chapter9.html)

Prefix for a sumti, indicating which numbered place in the place structure the
sumti belongs in; overrides word order.

fa mi cu klama fi la .atlantas. fe la bastn. fo le dargu fu le karce x1= I go
x3= Atlanta x2= Boston x4= the road x5= the car. I go from Atlanta to Boston via
the road using the car.

