"Trying to solve [differential] equations is a youthful aberration that you will soon grow out of."
While on the subject how about this fundamental law of physics heard in General Relativity this year: "Nature abhors second order differential equations."
This year's Modesty Prize is awarded to the lecturer who said : "Of course,this isn't really the best way to do it. But seeing as you're not quite as clever as I am-in fact none of you are anywhere near as clever as I am-we'll do it this way."
From the same lecturer : "Now we'll prove the theorem.In fact I'll prove it all by myself."
From a supervisor: "Any theorem in Analysis can be fitted onto an arbitrarily small piece of paper if you are sufficiently obscure."
Why do mathematicians insist on using words that already have another meaning? "It is the complex case that is easier to deal with."
And from various seminars in the King's College Research Centre: "...the non-uniqueness is exponentially small." "I'm not going to say exactly what I mean because I'm not absolutely certain myself." "It's dangerous to name your children until you know how many you are going to have." "You don't want to prove theorems that are false." And that last one wins the Sybil Fawlty Prize for "Stating the Bleeding Obvious".
A slightly more honest version of "The student can easily see that..." : "If you play around with your fingers for a while, you'll see that's true."
Suggestions are welcome on the meaning of this: "If it doesn't happen at a corner, but at an edge, it nonetheless happens at a corner."
Good heavens, do I see a lecturer actually noticing the existence of his audience! "Was that clear enough? Put up your hand if that wasn't clear enough. Ah, I thought not."
"You could define the subspace topology this way, if you were sufficiently malicious."
From 1A NatSci "Cells" course: " There are two proteins involved in DNA synthasis, they are called DNAsynthase 1 and DNAsynthase 3"
"Apart from the extra line that's a one line proof."
"This is a one line proof...if we start sufficiently far to the left."
"And before I leave this subject, I would like to tell you something interesting."
From a first year chemistry lecture some personal problems of the lecturer: "Before I started this morning's lecture I was going to tell you about my third divorce but on reflection I thought I'd better tell my wife first."