This is the 8552nd most frequent Chinese word.
tfsi
It seems "tfsi" is not a Chinese word; it is likely a term related to Audi's engine technology ("Turbo Fuel Stratified Injection"). No Chinese definition applies.
TFSI here represents a specific technological term.
TFSI是奥迪汽车的一种发动机技术。
TFSI is a type of engine technology used in Audi vehicles.
TFSI is used as a subject of inquiry.
小明问老师，TFSI是什么含义？
Xiaoming asked the teacher, 'What does TFSI mean?'
TFSI is used contextually as a feature associated with vehicles.