GLOSSARY OF SELECTED TERMS Below are certain acronyms, concepts and defined terms commonly used in our industry and in this QuarterlyReport on Form 10-Q, along with their meanings: GENERAL Unless the context otherwise indicates or requires, references in this Quarterly Report on Form 10-Q to “Adtran,”the “Company,” “we”, “us” and “our” refer to ADTRAN, Inc. and its consolidated subsidiaries prior to the mergerof Acorn MergeCo, Inc., a subsidiary of ADTRAN Holdings, Inc., with and into ADTRAN, Inc., on July 8, 2022,after which ADTRAN, Inc. became a wholly-owned direct subsidiary of ADTRAN Holdings, Inc. (“Merger”), andto ADTRAN Holdings, Inc. and its consolidated subsidiaries following the Merger. Furthermore, unless the context CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS The Private Securities Litigation Reform Act of 1995 provides a safe harbor for forward-looking statements madeby or on behalf of Adtran. Adtran and its representatives may from time to time make written or oral forward-looking statements, including statements contained in this report, our other filings with the SEC and othercommunications with our stockholders. Any statement that does not directly relate to a historical or current fact is aforward-looking statement. Generally, the words “believe”, “expect”, “intend”, “estimate”, “anticipate”, “would”,“will”, “may”, “might”, “could”, “should”, “can”, “future”, “assume”, “plan”, “seek”, “predict”, “potential”,“objective”, “expect”, “target”, “project”, “outlook”, “forecast” and similar expressions identify forward-lookingstatements. We caution you that any forward-looking statements made by us or on our behalf are subject touncertainties and other factors that could affect the accuracy of such statements. Forward-looking statements are Risks related to our financial results and Company success •We are obligated to comply with covenants related to our Wells Fargo Credit Agreement that couldrestrict our operating activities, and the failure to comply with such covenants could result in defaultsthat accelerate our debt obligations.•Wehave experienced significant fluctuations in revenue and such fluctuations may continue.Fluctuations in revenue can cause our operating results in a given reporting period to be higher or lowerthan expected.•Accurately matching necessary inventory levels to customer demand within the current environment ischallenging, and we may incur additional costs or be required to write off significant inventory thatwould adversely impact our results of operations.•The lengthy sales and approval process required by Service Providers for new products has resulted influctuations in our revenue and may result in future revenue fluctuations.•We require a significant amount of cash to service our indebtedness, our payment obligations to AdtranNetworks shareholders under the DPLTA, and other obligations.•The terms of the DPLTA may have a material adverse effect on our financial results and condition.•Our significant indebtedness exposes us to various risks.•We depend heavily on sales to certain customers; the loss of any of these customers or a significant •Managing our inventory is complex and has included and may continue to include write downs of excessor obsolete inventory.•Our international operations have and may continue to expose us to additional risks, increase our costsand adversely affect our operating results, financial condition and cash flows.•Our success depends on attracting and retaining key personnel.•We are exposed to adverse currency exchange rate fluctuations in jurisdictions where we transact in localcurrency, which could harm our financial results and cash flows.•We have recognized impairment charges related to goodwill and other intangible assets in the past and Risks related to our control environment •We have had to restate our previously issued consolidated financial statements and, as part of thatprocess, have identified material weaknesses in our internal control over financial reporting. If we areunable to develop and maintain effective internal control over financial reporting, we may not be able toaccuratelyreport our financial results in a timely manner,which may adversely affect investor confidence in us and may adversely affect our business, financial condition and results of operations.•We may face litigation and other risks as a result of our material weaknesses in our internal control overfinancialreporting and any resulting restatement of our previously issued consolidated financial statements. Risks related to the telecommunications industry •We must continue to update and improve our products and develop new products to compete and to keeppace with improvements in communications technology.•Our failure or the failure of our contract manufacturers to comply with applicable environmentalregulations could adversely impact our results of operations.•If our products do not interoperate with our customers’ networks, installat