Describe the desired features of a "Mathematics Colloquium"? I'm now a member of my department's colloquium committee.  Our task is to make a great colloquium series. I thought that the first step would be to come up with an appropriate definition of "Mathematics Colloquium." Standard dictionaries are not too much help:
Colloquium: n. 
 1. A usually academic meeting at which specialists deliver
    addresses on a topic or related topics and then answer questions relating to them.
 2. A conference at which scholars or other experts present papers on, analyze, 
    and discuss a specific topic.

So here's my question: What is the ideal definition of a mathematics colloquium?  Of course I know a bunch of things that make for bad colloquium talks, so I'm interested in knowing the definition of a good or great mathematics colloquium. 
 A: A great mathematics colloquium is one which satisfies many if not all of its goals, and may have additional benefits which make it great.
A list of potential goals/benefits:


*

*accessibility: many if not all attendees can understand a talk

*entertainment: attendees enjoy or find the presentation enjoyable

*breadth: the collection of topics covers a wide range of interests

*thematic: there is a common thread or other connection which relates the
different talks and draws connections

*stimulating: encourages audience members to discuss and extend the subject matter
outside the colloquium

*durable:  the recording made is archive quality and can be shared with others

*effective: members of the audience can take some of the main ideas and recapitulate them for others who were not at the colloquium, and make the others understand the ideas.


Of the list above, I value being effective more highly than the other items.
Gerhard "What Are Your Colloquium Goals?" Paseman, 2015.06.07
A: Some suggestions:


*

*Let all faculty members in turn choose speakers to invite.
This ensures that everybody gets involved, and that the interests
of all faculty members are represented.

*Choose a room / building in which people feel well
(this is underestimated sometimes!), and choose a time where people
have time to attend and do not need to rush to their lectures
once the talk is over.

*After the colloquium talks, always have a joint lunch / coffee / supper
(depending on the time of the day) in some pub / restaurant etc..
This fosters discussion among faculty members working on different
fields, and with the speakers. Try to choose a different location for this
every time.

*As others have already said, tell speakers to give talks
which all faculty members can understand -- and not only
specialists in the respective field.
