  Exceptional point (EP) is exclusive for non-Hermitian system and distinct
from that at a degeneracy point (DP), supporting intriguing dynamics, which can
be utilized to probe quantum phase transition and prepare eigenstates in a
Hermitian many-body system. In this work, we investigate the transition from DP
for a Hermitian system to EP driven by non-Hermitian terms. We present a
theorem on the existence of transition between DP and EP for a general system.
The obtained EP is robust to the strength of non-Hermitian terms. We illustrate
the theorem by an exactly solvable quasi-one-dimensional model, which allows
the existence of transition between fully degeneracy and exceptional spectra
driven by non-Hermitian tunnelings in real and k spaces, respectively. We also
study the EP dynamics for generating coalescing edge modes in
Su-Schrieffer-Heeger-like models. This finding reveals the ubiquitous
connection between DP and EP.
