What would a friendly introduction to something be? There are lots of friendly introductions to mathematical topics - number theory, single and multivariable, differential equations, abstract algebra, cross-entropy loss, and so on.
There's no definition popping up, just the phrase used over and over. it is also targeted towards "a good introduction" as in how to introduce someone, yourself, etc.
In mathematics I don't imagine it is affectionate, affable, amiable, genial, cordial, etc. What about favourable, advantageous, beneficial, benevolent and helpful?
Far down the list of definitions is the one that applies to our mathematics topics - it is easy to use or understand - friendly computer software or reader-friendly layout. Can you imagine an antagonistic or hostile approach to abstract algebra? Maybe that's how people think it currently is.
There are dandelions back on the scene - their last hurrah of the season.
