Roger Federer was fined $3,000 for using an audible obscenity during his Australian Open quarter-final victory over American Tennys Sandgren, tournament organisers said on Wednesday.
The Swiss was handed a code violation for swearing in the third set of Tuesday's match after the lineswoman reported Federer to Serbian chair umpire Marijana Veljovic.
Federer clarified in his post-match news conference that he had sworn in a "a mix" of languages and said he was frustrated by the way he received the on-court warning.
"Clearly she speaks mixed. Didn't know that. Next time I got to check the (language skills of the) lines-people," the 20-times Grand Slam champion said.
"Honestly, to be frustrated at one point... I think it's normal.
"I found it a bit tough. It's not like I'm known to throw around words and whatever. It's not like the whole stadium heard it either."
Federer went on to save seven match-points against Sandgren before winning in five sets to set up a semi-final clash with defending champion Novak Djokovic.
