**Corrado Segre** was an Italian mathematician who was responsible for important early work in algebraic geometry.

- The young Corrado completed his secondary education at the Sommeiller Technical Institute in Turin where he had Giuseppe Bruno as a mathematics teacher.
- At this time Giuseppe Bruno was also teaching descriptive geometry at the University of Turin and he gave the young Segre a great love of geometry.
- Segre, only 16 years old, was awarded his diploma and received a prize of 300 lire from the Chamber of Commerce for being ranked first in his class at the Technical Institute.
- Gino Loria, who was to write famous texts on the history of mathematics, was a fellow student of Segre's and they remained friends throughout their lives.
- In his fourth and final year of study (1882-83), in addition to the compulsory courses on Higher Mechanics, Astronomy and Mathematical Physics, Segre again followed the course of higher geometry given by D'Ovidio and the analysis course by Faà di Bruno.
- Segre fully understood the importance of mastering both the geometrical methods as well as those of analysis.
- the two closely connected works remain surprised by the confidence and breadth of vision and mathematical means with which this young man, Corrado Segre, deals with this broad topic.
- Even before he had completed his thesis, Segre had sent the paper Sur les différentes espèces de complexes du 2 degré des droites qui coupent hamoniquement deux surfaces du second ordre Ⓣ(On the various complex kinds of degree 2 of lines that intersect hamonically two surfaces of the second order) to Felix Klein for publication in Mathematische Annalen.
- The paper appeared in 1883 and it started a correspondence between Segre and Klein which they actively pursued for many years.
- Another young mathematician at Turin, five years older than Segre, was Giuseppe Peano.
- in the mid 1880's, these two very young researchers, Segre and Peano, both of them only just past twenty and both working at the University of Turin, were developing very advanced points of view on fundamental geometrical issues.
- In 1885 Segre was appointed as assistant to Giuseppe Bruno who held the chair of projective and descriptive geometry.
- Appointments to chairs were by competition and, in 1888, Segre entered the competition for the new chair of higher geometry in Turin.
- The interaction between Segre and Klein saw Segre become enthusiastic for Klein's 'Erlangen Programme'.
- Segre convinced one of the students at Turin, Gino Fano, to make a translation which was published in 'Annali di Mathematische' in 1890.
- In 1891 Segre went on an extended tour of Germany visiting the mathematical centres of Göttingen, Frankfurt, Nuremberg, Leipzig and Munich.
- It is a fascinating article, both for the advice it gives young people and also for the insight it gives us into Segre's thinking about geometrical research.
- With regard to rigour, Segre recommends the geometer to be as rigorous as he can, and to own up like a man when he makes use of methods of doubtful parentage.
- Later in his career, Segre took on administrative positions in the university.
- On the other side, Veronese and Bertini at first, and then Corrado Segre were perfectly aware that not only the geometry of hyperspaces would shed new light on the geometry of curves and surfaces of ordinary space, but also that these latter could be viewed - and this is certainly innovative - as points (defined by a number of parameters) belonging to new algebraic varieties that could not be placed in ordinary space.
- Segre worked on geometric properties invariant under linear transformations, algebraic curves and ruled surfaces studying transformations already considered by Alexander von Brill, Alfred Clebsch, Paul Gordan and Max Noether.
- Using the methods which he had introduced, Segre was able to study Kummer's surface in a much simpler way.
- In a paper published in 1896, Segre found an invariant of surfaces under birational transformations which had appeared in a different form in a 1871 article by Zeuthen: this invariant is now called the Zeuthen-Segre invariant.
- In 1890 Segre looked at properties of the Riemann sphere and was led to a new area of representing complex points in geometry.
- Motivated by the works of von Staudt, Segre considered a different type of complex geometry in 1912.
- Among other important work which Segre produced was an extension of ideas of Darboux on surfaces defined by certain differential equations.
- Segre was one of only four invited plenary speakers at the International Congress of Mathematicians held in Heidelberg in August 1904.
- Segre's contribution to the knowledge of space assures him a place after Cremona in the ranks of the most illustrious members of the new Italian school of geometry.
- Segre received many honours and we mention some of them.
- His achievements have been recognised recently with the conference 'Homage to Corrado Segre (1863-1924)' which was held in Turin in November 2013 to celebrate his 150th birthday.
- Moreover Corrado Segre is regarded as a crucial figure in the scientific evolution and in the history of Algebraic Geometry.
- Finally, we give several accounts of Segre as a teacher.

Born 20 August 1863, Saluzzo, Italy. Died 18 May 1924, Turin, Italy.

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Origin Italy

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive