Exhibit 99.1

                                Explanatory Note

(1)      Represents the exchange of limited liability company units ("LLC
Units") of AIDH Topco, LLC ("Definitive OpCo"), a subsidiary of the Issuer,
together with the cancellation of an equal number of the Issuer's Class B
Common Stock for shares of the Issuer's Class A Common Stock on a one-for-one
basis. The LLC Units exchanged and an equal number of shares of Class B Common
Stock cancelled by each Spectrum Fund (as defined below) are as follows: (i)
2,710,803 by SE VII DHC AIV, L.P. ("SE VII DHC AIV"), (ii) 3,939 by Spectrum
VII Investment Managers' Fund, L.P. ("Spectrum VII Investment Managers' Fund")
and (iii) 2,301 by Spectrum VII Co-Investment Fund, L.P. ("Spectrum VII Co-
Investment Fund").

(2)      The Second Amended and Restated Limited Liability Company Agreement of
Definitive OpCo permits holders of LLC Units to exchange their LLC Units for
shares of Class A Common Stock on a one-for-one basis, subject to certain
exceptions, conditions and adjustments. At the time of any such exchange, an
equal number of shares of Class B Common Stock of the Issuer held by the
Reporting Persons, which have no economic value and entitle holders thereof to
one vote per share on all matters on which stockholders of the Issuer are
entitled to vote generally, are cancelled. The LLC Units have no expiration
date.

(3)      SEA VII Management, LLC ("Spectrum") manages the Spectrum Funds (as
defined below) that collectively own, following the reported transactions,
1,743,478 shares of Class A Common Stock of the Issuer and 16,741,337 shares of
Class B common stock of the Issuer, which are represented as follows: (i)
1,743,478 shares of Class A Common Stock held directly by SE VII DHC AIV
Feeder, L.P. ("Spectrum Feeder" and together with SE VII DHC AIV, Spectrum VII
Investment Managers' Fund and Spectrum VII Co-Investment Fund, the "Spectrum
Funds"), (ii) 16,702,890 shares of Class B Common Stock held directly by SE VII
DHC AIV; (iii) 24,270 shares of Class B Common Stock held directly by Spectrum
VII Investment Managers' Fund; and (iv) 14,177 shares of Class B Common Stock
held directly by Spectrum VII Co-Investment Fund. Spectrum is the general
partner of Spectrum Equity Associates VII, L.P., which in turn is the general
partner of each of the Spectrum Funds. Each Reporting Person disclaims Section
16 beneficial ownership of the shares reported herein except to the extent of
its pecuniary interest therein, if any, and the inclusion of these shares in
this report shall not be deemed an admission of beneficial ownership of any of
the reported shares for purposes of Section 16 or any other purpose.

(4)      Represents a pro rata distribution in kind of the Issuer's Class A
Common Stock for no consideration to limited partners by the Spectrum Funds in
the following amounts: (i) 282,957 shares by Spectrum Feeder and (ii) 2,710,803
shares by SE VII DHC AIV. The other Spectrum Funds did not distribute any
shares of Class A Common Stock.

(5)      Represents the sale of shares of Class A Common Stock by Spectrum VII
Co-Investment Fund. The price reported in Column 4 is a weighted average price.
These shares were sold in multiple transactions at prices ranging from $9.01 to
$9.14, inclusive. The Reporting Persons undertake to provide to Definitive
Healthcare Corp., any security holder, or the staff of the Securities Exchange
Commission, upon request, full information regarding the number of shares sold
at each separate price within the ranges set for in footnotes (5) and (6) to
Form 4.

(6)      Represents the sale of shares of Class A Common Stock by Spectrum VII
Investment Managers' Fund. The price reported in Column 4 is a weighted average
price. These shares were sold in multiple transactions at prices ranging from
$9.01 to $9.14, inclusive.